Thermal Determinants of Nest Site Selection in Loggerhead Sea

University of South Florida Scholar Commons

Graduate Theses and Dissertations Graduate School

January 2012 Thermal Determinants of Nest Site Selection in Loggerhead Sea Turtles, Caretta caretta, at Casey Key, Florida Lindsey Nicole Flynn University of South Florida, [email protected]

Follow this and additional works at: http://scholarcommons.usf.edu/etd Part of the Other Oceanography and Atmospheric Sciences and Meteorology Commons

Scholar Commons Citation Flynn, Lindsey Nicole, "Thermal Determinants of Nest Site Selection in Loggerhead Sea Turtles, Caretta caretta, at Casey Key, Florida" (2012). Graduate Theses and Dissertations. http://scholarcommons.usf.edu/etd/4323

This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected].

Thermal Determinants of Nest Site Selection in Loggerhead Sea Turtles, Caretta caretta,

at Casey Key, Florida

Lindsey Flynn

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science College of Marine Science University of South Florida

Co-Major Professor: Edward S. Van Vleet, Ph.D. Co-Major Professor: Anton D. Tucker, Ph.D. Deby Cassill, Ph.D. Albert C. Hine, Ph.D.

Date of Approval: November 6, 2012

Keywords: Temperature, Reproductive Biology, Infrared Thermometer, Thermocouple Probe, Environmental Cues, Sediment, Weather, Slope

DEDICATION

I would like to dedicate this thesis to Nathan. You have been my rock. Your emotional strength has pulled me out of my lowest points and inspired me to keep going.

You are my better half and I love you.

I would like to thank my parents for supporting my dreams of working in the marine science field from the moment we moved to Florida in 1991. You never doubted my abilities or my dedication and I thank you every day for that. Your love and support have meant everything to me. To my siblings, thank you for believing me, even when we did not always see eye to eye. I would also like to thank Dr. Deby Cassill for giving me a chance to learn as an undergraduate and assisting me in continuing my education as a graduate student. You have an enthusiasm for learning that is unparallel and contagious.

Thank you for passing some of that on to me. To Dr. Ted Van Vleet and Dr. Tony

Tucker, thank you for taking a chance on me. You both pushed me to produce the best work that I could and I appreciate that. Your unwavering support and guidance inspired me to do my very best with this project. I hope I have made you both proud.

Finally to the other two parts of the “Three Musketeers”, Monica and Mark, you helped me get through some tough times. You said what I needed to hear and made me laugh when I needed it most. I could not have asked for better people in my life.

ACKNOWLEDGMENTS

These studies were conducted in accordance with Florida Fish and Wildlife

Conservation Commission Marine Turtle Permit 155 and Mote IACUC 10-03-AT1.

Research equipment and overall support was enabled by Mote Marine Laboratory’s Sea

Turtle Conservation and Research Program and the University of South Florida’s College of Marine Science. I thank A. Oeding, L. Ranalli, and all other interns and staff members at Mote Marine Laboratory’s STCRP for field assistance on Casey Key. I thank T. Flynn and E. Flynn for generously providing field accommodations. Additional temperature data were collected and provided by Michael Frick of Wassaw Caretta Research Project,

David Addison of Keewaydin Island Turtle Project, and Dr. Tony Tucker, director of

Mote Marine Laboratory’s Sea Turtle Conservation and Research Program. I thank Dr.

Tucker for the opportunity to perform research at Mote Marine Laboratory, and being an invaluable source of inspiration and sea turtle knowledge. Thank you to Dr. Ted Van

Vleet and Dr. Deby Cassill for constant and patient guidance with statistical analysis and writing. Additional thanks go to Dr. Armando Hoare of University of South Florida for providing support during statistical analysis.

TABLE OF CONTENTS

List of Tables ...... iv

List of Figures ...... vi

Abstract ...... xi

Chapter One: Introduction ...... 1 Effects of Beach Characteristics on Nest Site Selection ...... 6 Significance of Temperature on Nest Site Selection ...... 13 Objectives ...... 14

Chapter 2: Methods ...... 15 Study Site ...... 15 Data Collection ...... 17 Nests and False Crawls ...... 21 Neophytes and Remigrants ...... 21 Environmental Parameters ...... 22 Thermal Transect Data Collection ...... 23 Rookery Contrasts ...... 23 Statistical Analysis ...... 24

Chapter 3: Results ...... 26 Correlation Between IR and Thermocouple Thermometers ...... 26 Thermal Comparison Between Nesting and False Crawling Females...... 26 2008 Nesting Season ...... 26 2009 Nesting Season ...... 28 Comparison Between Seasons ...... 28 Thermal Comparison Among Nest Locations and Other Beach Locations ...... 30 2008 Nesting Season ...... 30 False Crawl Events ...... 30 Nest Events ...... 32 Adjacent to the Crawl Tracks ...... 35 2009 Nesting Season ...... 35 Within the Crawl Tracks ...... 35 Adjacent to the Crawl Tracks ...... 37 Comparisons of Mean Temperatures Between the 2008 and 2009 Nesting Seasons ...... 38 Mean Temperatures of the Sediment and Water...... 38 Within the Crawl Tracks ...... 38

i Adjacent to the Crawl Tracks ...... 41 Mean Temperatures of the Nest Site ...... 42 Within the Crawl Tracks ...... 42 Adjacent to the Crawl Tracks ...... 43 Effect of Weather on Mean Temperatures of the Sediment and Nest Site ...... 44 2008 Nesting Season ...... 44 Within the Crawl Tracks ...... 44 Rain ...... 44 Cloud Cover ...... 46 Wind ...... 48 Adjacent to the Crawl Tracks ...... 49 Rain ...... 49 Cloud Cover ...... 50 Wind ...... 51 2009 Nesting Season ...... 53 Within the Crawl Tracks ...... 53 Rain ...... 53 Cloud Cover ...... 53 Wind ...... 54 Adjacent to the Crawl Tracks ...... 56 Cloud Cover ...... 56 Wind ...... 57 Correlation Between Beach Slope and Distance ...... 57

Chapter 4: Discussion ...... 58 IR vs. Thermocouple Comparisons...... 58 Thermal Relationships: 2008 and 2009 on Casey Key ...... 59 Weather and Temperature Relationships: 2008 and 2009 ...... 65 Slope as a Cue for Nest Site Selection ...... 67 Case Study 1: Serial Measurements of a Remigrant Loggerhead...... 70 Thermal Relationships ...... 70 Weather ...... 72 Case Study 2: Serial Measurements of a Neophyte Loggerhead ...... 74 Thermal Relationships ...... 74 Weather ...... 75 Supplementary Thermal Data Retrieved from Additional Loggerhead Rookeries ...... 76

Chapter 5: Broader Implications and Conclusions ...... 78 Broader Implications ...... 78 Conclusions ...... 82

List of References ...... 86

Appendix 1: Additional Figures...... 94

ii Appendix 2: Casey Key 2007 ...... 100 Thermal Relationships ...... 100 Weather ...... 105

Appendix 3: Casey Key: Thermal Differences Over Three Years ...... 108 Gular Skin Temperature ...... 108 False Crawl Events ...... 108 Nest Events ...... 111

Appendix 4: Temperatures of Beaches When Turtles Were Not Present ...... 119

Appendix 5: Little Cumberland Island- 1982 ...... 122

Appendix 6: Wreck Island- 2005 ...... 127

Appendix 7: Keewaydin Island- 2007 ...... 130

Appendix 8: Wassaw Island- 2008 and 2009 ...... 133 2008 Nesting Season ...... 133 2009 Nesting Season ...... 135 False Crawl Events ...... 135 Nest Events ...... 137 Wassaw Island: 2008 vs. 2009 ...... 139

iii

LIST OF TABLES

Table 1: Synthesis of nest site selection references related to physical or environmental attributes...... 3

Table 2: Synthesis of nest site selection references related to nesting beach attributes ...... 7

Table 3: Synthesis of nest site selection references related to nesting beach sediment parameters...... 10

Table 4: Percentage of sediment sieved from the mean high water mark (MHW), mid beach (MID) and toe of the beach (TOE) on Casey Key from 2004 to 2006 for seven sizes of particles, in both millimeters and phi size ...... 18

Table 5: Mean temperatures of all false crawl and nesting events measured on Casey Key in 2008 and 2009...... 30

Table 6: List of all abbreviations for beach locations measured in the study and their meanings ...... 33

Table 7: Mean temperatures of all locations measured within and one meter adjacent to the crawl tracks of both false crawl events and nest events on Casey Key in 2008 ...... 34

Table 8: Mean temperatures of all locations measured within and one meter adjacent to the crawl tracks of both false crawl events and nest events on Casey Key in 2009 ...... 37

Table 9: Mean water and sand temperatures measured within and one meter adjacent to the crawl tracks of false crawl and nest events, including p- values of relevant statistical tests conducted between the 2008 and 2009 nesting seasons on Casey Key ...... 39

Table 10: Mean temperatures within and one meter adjacent to the nest site and p-values of relevant statistical tests conducted between the 2008 and 2009 nesting seasons on Casey Key ...... 47

iv Table A1: Mean temperatures of all locations measured within and one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2007 ...... 102

Table A2: Mean temperatures of the sediment and nest locations within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009 ...... 111

Table A3: Mean temperatures of the sediment and nest locations one meter adjacent to the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009 ...... 112

Table A4: Mean sediment temperatures obtained during the 2009 nesting season within and one meter adjacent to five profiles from four beaches closest to the study site (South Casey Key) known to host loggerhead turtle nesting...... 121

Table A5: Mean temperatures of all locations measured within the crawl tracks of false crawl and nest events on Little Cumberland Island (1982), Wreck Island (2005), Keewaydin Island (2007) and Wassaw Island (2008, 2009) ...... 124

LIST OF FIGURES

Figure 1: Map of Florida, where “A” indicates the location of Casey Key (retrieved from Google Maps) ...... 16

Figure 2: Photo of Casey Key (taken by Lindsey Flynn) ...... 17

Figure 3: Histogram of total data points collected by month for the 2008 and 2009 nesting seasons on Casey Key ...... 19

Figure 4: Histogram of data points collected by day of the week for both the 2008 and 2009 nesting seasons on Casey Key...... 20

Figure 5: Distribution of temperature data (using IR thermometer) within the crawl tracks of the adult female loggerhead turtles collected on Casey Key in 2008 and 2009 (n = 1462) ...... 25

Figure 6a: Linear regressions comparing surface temperature data collected using an IR thermometer and temperature data collected at 2cm depth using a thermocouple probe (a) within the crawl tracks and (b) one meter adjacent to the crawl tracks, on Casey Key in 2009 ...... 27

Figure 6b: Linear regressions comparing surface temperature data collected using an IR thermometer and temperature data collected at 2cm depth using a thermocouple probe (a) within the crawl tracks and (b) one meter adjacent to the crawl tracks, on Casey Key in 2009 ...... 27

Figure 7: Box plot of a thermal comparison between false crawl and nesting events on Casey Key in 2008 ...... 29

Figure 8a: Box plots of thermal comparisons of all nesting events collected (a) within the crawl tracks and (b) one meter adjacent to the crawl tracks on Casey Key in 2008 and 2009 ...... 31

Figure 8b: Box plots of thermal comparisons of all nesting events collected (a) within the crawl tracks and (b) one meter adjacent to the crawl tracks on Casey Key in 2008 and 2009 ...... 31

Figure 9: Box plot of the mean water temperatures within the crawl tracks of nest events on Casey Key in 2008 and 2009...... 40

vi Figure 10: Box plot of the mean waterline temperatures within the crawl tracks of nest events on Casey Key in 2008 and 2009 ...... 41

Figure 11: Box plot of the mean dry sand temperatures within the crawl tracks of nest events on Casey Key in 2008 and 2009 ...... 42

Figure 12: Box plot of the mean water temperature one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2008 and 2009...... 43

Figure 13: Box plot of the mean waterline temperature one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2008 and 2009...... 44

Figure 14: Box plot of the mean dry sand temperature one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2008 and 2009...... 45

Figure 15: Box plot of the mean temperature of the surface of the eggs laid in nests on Casey Key in 2008 and 2009 ...... 46

Figure 16: Box plot of the mean temperature of the sediment one meter adjacent to the body pit of nests on Casey Key in 2008 and 2009 ...... 48

Figure 17: Box plot of the mean temperature of the sediment one meter adjacent to the eggs laid in nests on Casey Key in 2008 and 2009 ...... 49

Figure 18: Box plot of the mean temperature of the sediment one meter adjacent to the gular skin of the nesting females on Casey Key in 2008 and 2009...... 50

Figure 19: Box plot of the mean temperatures of wet and dry sand (combined within each condition, N and Y) within the crawl tracks of nesting events according to the absence (N) and presence (Y) of rain on Casey Key in 2008 ...... 51

Figure 20: Box plot of the mean temperature of the surface of the gular skin of nesting females in the absence (N) and presence (Y) of rain on Casey Key in 2008 ...... 52

Figure 21: Box plot of the mean temperature of wet and dry sand (combined within each condition, N and Y) within the crawl tracks of false crawl events according to the absence (N) and presence (Y) of cloud cover on Casey Key in 2008 ...... 53

vii Figure 22: Box plot of the mean temperature of wet and dry sand (combined within each condition, N and Y) one meter adjacent to the crawl tracks of false crawl and nesting events in the absence (N) and presence (Y) of rain on Casey Key in 2008 ...... 54

Figure 23: Box plot of the mean temperature of the sediment one meter adjacent to the body pit, nest chamber, eggs, and gular skin of the female (combined within each condition, N and Y) for nesting events in the absence (N) and presence (Y) of rain on Casey Key in 2008 ...... 55

Figure 24: Box plot of the mean temperature of wet and dry sand (combined within each condition, N and Y) one meter adjacent to the crawl tracks of both false crawl and nesting events in the absence (N) and presence (Y) of cloud cover on Casey Key in 2008 ...... 56

Figure 25: Box plot of the mean temperatures of the body pit attempt made closest to the nest site (BP2) and the gular skin of the turtle (GULAR) within the crawl tracks of nest events on Casey Key in 2008...... 62

Figure 26: Box plot of the mean temperatures of the sediment and water within the crawl tracks of nest events on Casey Key in 2008 ...... 63

Figure 27: Box plot of the mean temperatures of the sediment and water within the crawl tracks of both false crawl and nest events on Casey Key in 2009...... 64

Figure 28: Box plot of the mean temperature of all locations measured within crawl tracks of nest events made by Wiblet on Casey Key in 2008 and 2009 ...... 72

Figure 29: Box plot of the mean temperature of all locations measured one meter adjacent to the crawl tracks of nest events made by Wiblet on Casey Key in 2008 and 2009 ...... 73

Figure A1: Box plot of the mean temperatures of all locations measured within the crawl tracks of all false crawl events measured on Casey Key in 2008...... 94

Figure A2: Box plot of the mean temperatures of all locations measured within the crawl tracks of all nest events measured on Casey Key in 2008 ...... 95

Figure A3: Box plot of the mean temperatures of all locations measured one meter adjacent to the crawl tracks of both false crawl and nest events on Casey Key in 2008 ...... 96

viii Figure A4: Box plot of the mean temperatures of all locations measured within the crawl tracks of both false crawl and nest events on Casey Key in 2009...... 97

Figure A5: Box plot of the mean temperatures of all locations measured one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2009 ...... 98

Figure A6: Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events completed by Wiblet on Casey Key in 2008...... 99

Figure A7: Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events on Casey Key in 2007 ...... 101

Figure A8: Box plot of the mean temperatures of wet sand and dry sand (combined within each condition, N and Y) within the crawl tracks of nest events according to the absence (N) and presence (Y) of cloud cover on Casey Key in 2007 ...... 106

Figure A9: Box plot of the mean temperatures of wet sand and dry sand (combined within each condition, N and Y) one meter adjacent to the crawl tracks of nest events according to the absence (N) and presence (Y) of cloud cover on Casey Key in 2007 ...... 107

Figure A10: Box plot of the mean temperature of dry sand within the crawl tracks of false crawl events on Casey Key in 2007 and 2008 ...... 109

Figure A11: Box plot of the mean water temperature within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009...... 112

Figure A12: Box plot of the mean waterline temperature within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009 ...... 113

Figure A13: Box plot of the mean dry sand temperatures within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009 ...... 114

Figure A14: Box plot of the mean temperatures of the body pit and nest chamber (combined within each year) of nests measured on Casey Key in 2007, 2008 and 2009 ...... 115

Figure A15: Box plot of mean egg temperatures within all nests measured on Casey Key in 2007, 2008 and 2009 ...... 116

ix Figure A16: Box plot of the mean temperature of all sediment locations measured within the profiles of five beaches known to host loggerhead turtle nesting in southwest Florida in 2009 ...... 120

Figure A17: Sand samples from five beaches in southwest Florida known to host loggerhead turtle nesting ...... 121

Figure A18: Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events on Little Cumberland Island, Georgia, USA in 1982 ...... 123

Figure A19: Box plot of the mean temperatures of the body pit (BP1), high tide line (HTL), and water (W) within the crawl tracks of all events measured on Wreck Island, Australia in 2005 ...... 128

Figure A20: Box plot of the mean temperatures of all locations measured within the crawl tracks of false crawl and nest events on Keewaydin Island, Florida, USA, in 2007 ...... 131

Figure A21: Box plot of the mean temperatures of all locations measured within the crawl tracks of all nest events measured on Wassaw Island, Georgia, USA in 2008...... 134

Figure A22: Box plot of the mean temperatures of all locations measured within the crawl tracks of all false crawl events measured on Wassaw Island, Georgia, USA in 2009 ...... 136

Figure A23: Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events measured on Wassaw Island, Georgia, USA in 2009 ...... 138

ABSTRACT

Many environmental cues are thought to influence nest site selection by loggerhead sea turtles, Caretta caretta, and much debate exists over the possible influence of sand temperature. This study had two primary objectives: (1) to measure thermal differences across transects of a major nesting beach of Casey Key (28.7 N, 82.3

W), Florida and (2) to evaluate thermal pattern variation that influenced nesting patterns of adult female loggerhead sea turtles. A secondary objective of this study was to determine the efficacy of infrared thermometers to collect sand surface temperatures in the field.

Temperature data were collected from 145 nest events and 8 false crawls in the

2008 and 2009 nesting seasons. Infrared thermometers and thermocouple probes were used to obtain surface temperatures from the water, waterline, beach sand, body pit attempts, nest chamber attempts, eggs, and the surface of the gular skin of the nesting female, within the crawl track created by the female and at one meter adjacent to the crawl track (from undisturbed sand). Weather influences at the time of nesting were recorded, including the presence or absence of rain, wind, or clouds. Beach slope was measured using an angle locator.

Temperature data from the infrared thermometer and the thermocouple probe were highly correlated, indicating that an infrared thermometer is an effective

xi measurement tool on a nesting beach. In 2008, there was a significant difference between temperatures collected within the crawl tracks of false crawl events and nest events, indicating a potential for females to use thermal cues in choosing whether to false crawl or nest. In both nesting seasons, the sand temperature in the body pit and the surface of the gular skin of the nesting female were nearly identical, suggesting females may locate a suitable nest site using their skin temperature. Data collected at other loggerhead rookeries in the United States and Australia yielded similar results, however, variability in the use of temperature may arise seasonally, and according to different nesting environments.

Rain, wind and cloud cover significantly thermally altered several locations on

Casey Key, but it remains unclear if these weather events significant affect turtle nesting behavior. Additionally, crawl distance and beach slope were significantly, positively correlated.

Gravid females most likely use multiple environmental cues to select a nest site.

Assimilating information from multiple sources allows for the highest degree of adaptability, and future studies should consider implications for climate change and beach renourishment projects.

xii

CHAPTER ONE – INTRODUCTION

Loggerhead sea turtles, Caretta caretta, live for decades at sea before beginning reproductive migrations. Estimations on the age of sexual maturity and the beginning of reproductive migrations for loggerheads in the southeastern United States range from 20 years (Mendonca, 1981 cited in Lutz et al., 2003; Frazer and Ehrhart, 1985 cited in Lutz et al., 2003; Conant et al., 2009) to more than 30 years (Frazer et al., 1994 cited in Lutz et al., 2003; NMFS, 2001 cited in Lutz et al., 2003). Once turtles reach nesting beaches, females emerge onto the nesting beach multiple times per nesting season to select nest sites. Loggerhead females deposit two to eight clutches in a single nesting season at intervals of 10-14 days (Caldwell, 1962 cited in Bolten and Witherington, 2003; Hughes and Mentis, 1967 cited in Bolten and Witherington, 2003; Talbert et al., 1980 cited in

Bolten and Witherington, 2003; Lenarz et al., 1981 cited in Bolten and Witherington,

2003; Limpus, 1985 cited in Bolten and Witherington, 2003; Lund, 1986 cited in Bolten and Witherington, 2003; Dodd, 1988 cited in Bolten and Witherington, 2003; Conant et al., 2009; Tucker, 2009). The sea turtle makes a decision on nest placement while operating temporarily in an unfamiliar terrestrial environment. Females leave the nest behind and will never know outcomes of terrestrial incubation, so any cues used to choose a nest site need not be reliable proxies about anything more than the immediate nesting episode. The key activity becomes a rapid search for functional cues on land that

1 a female can sense while briefly outside its usual marine habitat. The ability of the female to choose a satisfactory nest site is crucial because the choice affects embryo incubation period, embryo development and survivorship, hatchling sex ratios, hatching success, and parental fitness.

There are many studies of nest site selection in turtles and the divergent results seem to suggest that relative differences may emerge at specific beaches or alternatively that a broad array of nesting sites can be used. In fact, some studies dispute whether nest site selection occurs in turtles at all since consensus among nest site selection studies is rare. A model for loggerhead nesting on Sanibel and Captiva Islands in southwestern

Florida found nesting occurred randomly above the most recent high tide line (Table 1;

Hays et al., 1995). Leatherback nest distributions in Florida have also been shown to be insignificantly different from random (Table 1; Weishampel et al., 2003). However, other studies have suggested that nest locations were not randomly distributed based on available beach characteristics (Table 1; Camhi, 1993; Hays and Speakman, 1993; Wood and Bjorndal, 2000). Loggerhead and green turtle nesting and false crawl patterns have been shown to be non-random in Florida (Table 1; Weishampel et al, 2003). In addition, loggerhead turtles have been shown to lay their eggs in nonrandom patterns (Table 1;

Martin et al., 1989 cited in Bolten and Witherington, 2003; Mellanby et al., 1998 cited in

Bolten and Witherington, 2003).

Still others suggest that nest site selection is influenced by human activity.

Loggerhead nests on Dalaman-Sarigerme beach in Turkey were more concentrated on undeveloped parts of the beach, and much less concentrated in areas where recent building took place (Kaska et al., 2010). It has also been suggested that artificial lighting

Table 1. Synthesis of nest site selection references related to physical or environmental attributes. A “Y” indicates the reference affirms the attribute affects nest site selection of the turtle species indicated, and an “N” indicates the reference discounts the effect of the attribute on nest site selection of the turtle species.

Reference Species** Beach Location Random/ Scattered/ Nest Variable Placement Water Temperature Air Temperature Humidity Rain Wind CloudCover Cycle Tidal Barometric Pressure Stoneburner and Richardson, 1981 Cc Florida, USA – – – – – – – – – Martin et al., 1989 Cc Florida, USA N – – – – – – – – Camhi, 1993 Cc Georgia, USA N – – – – – – – – Hays and Speakman, 1993 Cc Greece N – – – – – – – –

Foley et al., 2000 Cc Florida, USA – – – – – – – – – Garmestani et al., 2000 Cc Florida, USA – – – – – – – – – Wood and Bjorndal, 2000 Cc Florida, USA – – – N – – – – – Mazaris et al., 2006 Cc Western Greece – – – – – – – – – Pike, 2008 Cc Florida, USA – Y Y – Y – – Y Y Florida, USA; Hays et al., 1995 Cc, Cm Ascension Island Y/N* – – – – – – – – Ackerman, 1997 – – – – – – – – – – – Mellanby et al., 1998 Cc, Cm Northern Cyprus N – – – – – – – – Cc, Cm, Weishampel et al., 2003 Dc Florida, USA Y/N* – – – – – – – – Serafini et al., 2009 Cc, Ei Bahia, Brazil – – – – – – – – – Cc, Cm, Northeastern Garcon et al., 2010 Nd, Ei, Dc Australia – – – – – Y – – –

Table 1 (cont.)

Reference Species** Beach Location Random/ Scattered/ Nest Variable Placement Water Temperature Air Temperature Humidity Rain Wind CloudCover Cycle Tidal Barometric Pressure Turkozan et al., 2011 Cc, Cm Turkey – – – – – – – – – Mrosovsky, 1983 Dc Malaysia; Guianas Y – – – – – – – – Johannes and Rimmer, 1984 Cm Western Australia – – – – – – – – – Whitmore and Dutton, 1985 Dc, Cm Suriname – – – – – – – – – Horrocks and Scott, 1991 Ei Barbados – – – – – – – – – South Carolina,

4 Burke et al., 1994 Ks USA – – – – Y – – – –

Blamires et al., 2003 Nd Western Australia – – – – – – – – – Spotila et al., 2003 Lo – – – – – – Y Y – – Wilson et al., 1999 Kb Florida, USA – – – – Y – – – – López-Castro et al., 2004 Lo Baja California – – – – – – – – – Southeastern Em, Ce, Australia; Illinois, Bowen et al., 2005 Cp USA – Y* Y* – Y* – – – – Kamel and Mrosovsky, 2005 Ei French West Indies – – – – – – – – – Caut et al., 2006 Dc French Guiana Y – – – – – – – – Kamel and Mrosovsky, 2006 Ei French West Indies – – – – – – – – – Chen et al., 2007 Cm Taiwan – – – – – – – – – Ficetola, 2007 Ei Qatar – – – – – – – – – Yalҫin-Özdilek et al., 2007 Cm Turkey – – – Y – – – – –

Table 1 (cont.)

Reference Species** Beach Location Random/ Scattered/ Nest Variable Placement Water Temperature Air Temperature Humidity Rain Wind CloudCover Cycle Tidal Barometric Pressure Spanier, 2010 Dc Costa Rica – – – – – – – – – *Preference is species specific **Cc = Caretta caretta; Ce = Chelodina expansa; Cm = Chelonia mydas; Cp = Chrysemys picta; Dc = Dermochelys coriacea; Ei = Eretmochelys imbricata; Em = Emydura macquarii; Kb = Kinosternon baurii; Ks = Kinosternon subrubrum; Lo = Lepidochelys olivacea; Nd = Natator depressus

(Witherington, 1992 cited in Bolten and Witherington, 2003) and the distance from the nearest human settlement (Kikukawa et al., 1998, 1999, cited in Bolten and Witherington,

2003) can influence nest site selection.

Effects of Beach Characteristics on Nest Site Selection

If nest site selection occurs in a nonrandom pattern, the environmental characteristics of the nesting beach have the potential to influence the decision process.

Hawksbill sea turtles, Eretmochelys imbricata, nesting in Trois Ilets and Folle Anse beaches in Guadeloupe, French West Indies tend to nest near or beneath low-lying vegetation or forest areas (Table 2; Kamel and Mrosovsky, 2005, 2006). Loggerhead turtle nests in Greece and Sanibel-Captiva Islands in Florida tend to be clumped near supra-littoral vegetation (Table 2; Hays and Speakman, 1993; Hays et al., 1995).

Loggerhead turtles nesting on the Ten Thousand Island in Florida nested on both open sand, near supra-littoral vegetation and within dense vegetation behind mangroves (Table

2; Foley et al., 2000; Garmestani et al, 2000). Similarly, green turtles, Chelonia mydas, in Suriname tend to nest in vegetated areas behind open sand (Table 2; Whitmore and

Dutton, 1985). Furthermore, green turtles nesting on Akyatan Beach, Turkey were found to nest most often in vegetated areas, while loggerhead turtles nested most commonly in nonvegetated areas, but there seemed to be annual variation in nest distribution (Table 2;

Turkozan et al., 2011).

The vegetation line has also been suggested to be the most important guide in the search for suitable nesting sites for green turtles on Wan-an Island, Taiwan, but proper

Table 2. Synthesis of nest site selection references related to nesting beach attributes. A “Y” indicates the reference affirms the attribute affects nest site selection of the turtle species indicated, and an “N” indicates the reference discounts the effect of the attribute on nest site selection of the turtle species.

Reference Species** Beach Location Vegetation Beach Open Beach Topography/ Slope Cover Rock Energy Wave Elevation Width Beach Stoneburner and Richardson, 1981 Cc Florida, USA – – – – – – – Martin et al., 1989 Cc Florida, USA – – – – – – – Camhi, 1993 Cc Georgia, USA – – – – – – – Hays and Speakman, 1993 Cc Greece Y – – – – – –

7 Foley et al., 2000 Cc Florida, USA Y Y – – – – –

Garmestani et al., 2000 Cc Florida, USA Y – Y – – – Y Wood and Bjorndal, 2000 Cc Florida, USA – – Y – – – – Mazaris et al., 2006 Cc Western Greece – – Y – – – Y Pike, 2008 Cc Florida, USA – – – – – – – Hays et al., 1995 Cc, Cm Florida, USA; Ascension Island Y* Y* Y* – – – – Ackerman, 1997 – – – – – – – – – Mellanby et al., 1998 Cc, Cm Northern Cyprus – – – – – – – Weishampel et al., 2003 Cc, Cm, Dc Florida, USA – – – – – – – Serafini et al., 2009 Cc, Ei Bahia, Brazil N Y/N* – – – – Y Cc, Cm, Garcon et al., 2010 Nd, Ei, Dc Northeastern Australia – – – – – – – Turkozan et al., 2011 Cc, Cm Turkey Y* Y* – – – – – Mrosovsky, 1983 Dc Malaysia; Guianas – – – – – – –

Table 2 (cont.)

Energy

Reference Species** Beach Location Vegetation Beach Open Beach Topography/ Slope Cover Rock Wave Elevation Width Beach Johannes and Rimmer, 1984 Cm Western Australia – – – – – Y – Whitmore and Dutton, 1985 Dc, Cm Suriname Y* Y* – – – – – Horrocks and Scott, 1991 Ei Barbados – – Y – Y Y – Burke et al., 1994 Ks South Carolina, USA – – – – – – – Blamires et al., 2003 Nd Western Australia – – Y – – – – Spotila et al., 2003 Lo – – – – – – – –

8 Wilson et al., 1999 Kb Florida, USA – – – – – – –

López-Castro et al., 2004 Lo Baja California – – – – – – – Bowen et al., 2005 Em, Ce, Cp Southeastern Australia; Illinois, USA – – – – – – – Kamel and Mrosovsky, 2005 Ei French West Indies Y – – – – – – Caut et al., 2006 Dc French Guiana – – – – – – – Kamel and Mrosovsky, 2006 Ei French West Indies Y – – – – – – Chen et al., 2007 Cm Taiwan Y – – – – – – Ficetola, 2007 Ei Qatar Y – Y Y – – – Yalҫin-Özdilek et al., 2007 Cm Turkey – – – – – – – Spanier, 2010 Dc Costa Rica – – Y – – – – *Preference is species specific **Cc = Caretta caretta; Ce = Chelodina expansa; Cm = Chelonia mydas; Cp = Chrysemys picta; Dc = Dermochelys coriacea; Ei = Eretmochelys imbricata; Em = Emydura macquarii; Kb = Kinosternon baurii; Ks = Kinosternon subrubrum; Lo = Lepidochelys olivacea; Nd = Natator depressus

vegetation cover, porewater content, and substratum compactness are important factors in the construction of the egg chamber (Table 2; Chen et al., 2007). In contrast, green turtles nesting on Ascension Island in the southern Atlantic Ocean tended to clump first digging attempts on the uneven beach above the spring high water line (Table 2; Hays et al., 1995). Similarly, leatherback turtles, Dermochelys coriacea, in Suriname tended to lay nests predominantly in open sand (Table 2; Whitmore and Dutton, 1985). However, hawksbills showed no nesting preference either for the sand or vegetation zones on

Arembepe Beach, Bahia, Brazil (Table 2; Serafini et al., 2009).

Vegetation and open sand are not the only two parameters that may influence nest site selection. Hawksbill nesting density in Rass Laffan, Qatar seems to be higher on beaches with little rock cover, soft soil, and high vegetation cover (Table 2; Table 3;

Ficetola, 2007). Hawksbills in Barbados tended to nest on beaches with low wave energy

(Table 2; Horrocks and Scott, 1991). These turtles also seemed to clump their nests around an elevation of 1.2 meters. Green turtles nesting on North West Cape Peninsula,

Western Australia, however, tended to nest on platforms of sand 1 to 3 meters above the mean high waterline (Table 2; Johannes and Rimmer, 1984).

Beach sand grain characteristics may also influence the female’s decision, as green turtles tend to nest on medium-sized sand grain beaches (353µm) in Turkey and turtle species prefer uniform sand compactness, a characteristic of natural beaches (Table

3; Ackerman, 1997; Yalçin-Özdilek et al., 2007). Yalçin-Özdilek et al. (2007) also suggest that green turtle nest sites have low humidity on the sand surface (Table 1).

Green turtles nesting in Australia seem to nest on beaches with low salinities in surface sand and at nest depth (Table 3; Johannes and Rimmer, 1984). Organic content of the

Table 3. Synthesis of nest site selection references related to nesting beach sediment parameters. A “Y” indicates the reference affirms the attribute affects nest site selection of the turtle species indicated, and an “N” indicates the reference discounts the effect of the attribute on nest site selection of the turtle species.

Reference Species** Beach Location Sand Temperature Sand/Soil Compactness Grain Sand Size Salinity of Sand Surface Organic Content Texture Sand ShellDebris Stoneburner and Richardson, 1981 Cc Florida, USA Y – – – – – – Martin et al., 1989 Cc Florida, USA – – – – – – – Camhi, 1993 Cc Georgia, USA N – – – – – –

1 Hays and Speakman, 1993 Cc Greece – – – – – – –

Foley et al., 2000 Cc Florida, USA – – – – – – – Garmestani et al., 2000 Cc Florida, USA – – – – – – Y Wood and Bjorndal, 2000 Cc Florida, USA N – – N – – – Mazaris et al., 2006 Cc Western Greece – – – – Y Y – Pike, 2008 Cc Florida, USA – – – – – – – Hays et al., 1995 Cc, Cm Florida, USA; Ascension Island – – – – – – – Ackerman, 1997 – – – Y – – – – – Mellanby et al., 1998 Cc, Cm Northern Cyprus – – – – – – – Weishampel et al., 2003 Cc, Cm, Dc Florida, USA – – – – – – – Serafini et al., 2009 Cc, Ei Bahia, Brazil – – – – – – – Cc, Cm, Garcon et al., 2010 Nd, Ei, Dc Northeastern Australia – – – – – – – Turkozan et al., 2011 Cc, Cm Turkey – – – – – – – Mrosovsky, 1983 Dc Malaysia; Guianas – – – – – – –

Table 3 (cont.)

Reference Species** Beach Location Sand Temperature Sand/Soil Compactness Grain Sand Size Salinity of Sand Surface Organic Content Texture Sand ShellDebris Johannes and Rimmer, 1984 Cm Western Australia – – – Y – – – Whitmore and Dutton, 1985 Dc, Cm Suriname – – – – – – – Horrocks and Scott, 1991 Ei Barbados – – – – – – – Burke et al., 1994 Ks South Carolina, USA – – – – – – – Blamires et al., 2003 Nd Western Australia – – – – – – – 11 Spotila et al., 2003 Lo – – – – – – – –

Wilson et al., 1999 Kb Florida, USA – – – – – – – López-Castro et al., 2004 Lo Baja California Y – – – – – – Bowen et al., 2005 Em, Ce, Cp Southeastern Australia; Illinois, USA – – – – – – – Kamel and Mrosovsky, 2005 Ei French West Indies – – – – – – – Caut et al., 2006 Dc French Guiana – – – – – – – Kamel and Mrosovsky, 2006 Ei French West Indies – – – – – – – Chen et al., 2007 Cm Taiwan – – – – – – – Ficetola, 2007 Ei Qatar – Y – – – – – Yalҫin-Özdilek et al., 2007 Cm Turkey – – Y – – – – Spanier, 2010 Dc Costa Rica – – – – – – – *Preference is species specific **Cc = Caretta caretta; Ce = Chelodina expansa; Cm = Chelonia mydas; Cp = Chrysemys picta; Dc = Dermochelys coriacea; Ei = Eretmochelys imbricata; Em = Emydura macquarii; Kb = Kinosternon baurii; Ks = Kinosternon subrubrum; Lo = Lepidochelys olivacea; Nd = Natator depressus

sand and sand texture can also be of moderate importance to nesting site selection (Table

3; Mazaris et al., 2006). However, at least one study refutes the possibility that moisture content and salinity may reliably influence nest site selection because they can vary over a short time scale and to a high degree as rainfall and the water table change (Table 1;

Table 3; Wood and Bjorndal, 2000).

Beach width may be an important cue for nesting turtles as well. A study on nesting female loggerhead sea turtles suggested that beach width is the most critical factor affecting nest site selection (Table 2; Mazaris et al., 2006). This species seems to prefer to nest in the sand zone, with the beach width positively influencing the distance crawled on the nesting beach and the width of the vegetated zone negatively influencing the distance the turtle travels (Table 2; Serafini et al., 2009). Loggerhead turtles nesting in Florida’s Ten Thousand Islands primarily prefer wide beaches as well and less shell debris (Table 2; Garmestani et al., 2000).

Differences in nesting preferences on various nesting beaches may be due to beach topography as well (Table 2; Ficetola, 2007). Green turtles nesting on Ascension

Island usually attempted to nest only after they reached the uneven beach above the spring high waterline (Table 2; Hays et al., 1995). Mazaris et al. (2006) found that and inclination of 15% in beach slope was a secondary factor used by turtles to choose a nest site, after beach width (Table 2). At a steeply sloped beach on the Atlantic coast of

Florida, slope was the most important environmental factor influencing nest site selection

(Table 2; Wood and Bjorndal, 2000). Beach slope increased significantly both near the waterline and nest locations. Similarly, Horrocks and Scott, 1991 suggested that hawksbills nesting in Barbados prefer to nest on more protected beaches (those less

exposed to heavy wave action) that had steeper slopes (Table 2). Other studies, however, have indicated that a gentle beach slope is the preferred characteristic for optimal nest locations. The greatest hawksbill nesting activity in Rass Laffan, Qatar was observed in areas with gentle slope, where dunes were far away from the coastline (Table 2; Ficetola,

2007). The wide beaches that loggerheads preferred to nest upon on Florida’s Ten

Thousand Islands were highly correlated with a decreased slope, which suggests that these turtles may prefer to nest on gently sloped beaches (Table 2; Garmestani, 2000).

Significance of Temperature on Nest Site Selection

Other debate continues over the possibility of sand temperature influencing nest site selection. Stoneburner and Richardson (1981) noted that loggerhead turtles typically traverse across cooler, wet beach as they first emerge onto the terrestrial environment, to a dry beach zone that becomes progressively warmer. In that study, as soon as a turtle experiences an abrupt temperature increase of two or three degrees Celsius in the dry sand, typically within a linear distance of 0.5 meters, it immediately begins to excavate a nest cavity (Table 3). Temperature was also an important cue in nest site selection for olive ridley sea turtles, Lepidochelys olivacea, nesting in Las Barracas, Baja California.

Turtles nesting on Las Barracas preferred places on the nesting beach where the temperature was close to 32°C (Table 3; López-Castro et al., 2004). In contrast, Wood and Bjorndal (2000) suggested that temperatures of track sites and nest sites were not significantly different and therefore, loggerheads do not look for an abrupt increase in temperature at all (Table 3). Similarly, loggerheads did not select nest sites in either

warmer or cooler patches of a heterogeneous beach on Cumberland Island, Georgia

(Table 3; Camhi, 1993). However, there may be multiple cues, and not just one major environmental factor, that influence or are even required for nest site selection, suggested by the varied findings of these previous nest site selection studies (Wood and Bjorndal,

2000; Mazaris et al., 2006; Pike, 2008).

Objectives

This study had two primary objectives: (1) to measure thermal differences across transects of a major nesting beach of Casey Key, Florida and (2) to evaluate thermal pattern variation that influences the nesting patterns of adult female loggerhead sea turtles. A secondary study objective was to determine the efficacy of infrared thermometers to collect sand surface temperatures in the field against a thermoprobe thermometer, which was the instrument used by earlier studies.

CHAPTER TWO – METHODS

Study Site

The study was conducted during patrols of the southern six kilometers of Casey

Key (28.7 N, 82.3 W), a barrier island located along on the southwestern coast of Florida between Sarasota and Venice (Fig. 1, Fig. 2). This beach has both public and private portions, such as public beach access, private homes, several small hotels and a fishing jetty at the southern end. Although beach front lighting at night issues can deter turtles from nesting (Witherington and Martin, 1996), the study site seldom had visible artificial lighting, with exceptions of hotels and a few large homes with exterior light fixtures.

Thus human interferences that might cause a turtle to false crawl were largely eliminated as an extraneous influence in the study.

Casey Key is a relatively low slope beach to the duneline, which consists of low sand dunes covered with sea oats (Uniola paniculata), beach sunflowers (Helianthus debilis), railroad vine (Ipomoea pes-caprae), and Australian pines (Casuarina equisetifolia). Temporary sand escarpments can be produced after a severe storm or tidal event, but berms are usually limited to approximately 1 to 0.5 meter(s) in height and usually restored within a few days.

Figure 1. Map of Florida, where “A” indicates the location of Casey Key (retrieved from Google Maps).

Sediment on Casey Key ranges from granules, the smallest gravel classification in the Udden-Wentworth classification scheme, to coarse silt, the largest silt classification

(Wentworth, 1922). Crushed shell and coral debris are also found on this beach.

Sediment grain analysis performed on Casey Key from 2004 to 2006 showed that the mean high water mark (MHW) on Casey Key consisted mostly of coarse sand grains one millimeter in size, sediment within the mid beach (MID) consisted mostly of medium-

sized sand grains 0.5 millimeters in size, and the toe of the dune (TOE) consisted mostly of fine sand grains 0.25 millimeters in size (Table 4; STCRP- unpublished data).

The portion of Casey Key used in this study typically supports 35 to 70 female loggerhead nests per kilometer per year, allowing for sufficient opportunity for data collection (Tucker, 2010).

Figure 2. Photo of Casey Key (taken by Lindsey Flynn).

Data Collection

Data were collected between 12 May and 31 July in the 2008 nesting season, and

17 May and 2 August in the 2009 nesting season, when the majority of loggerhead turtles were nesting (Fig. 3). The study site was patrolled nightly between 9:30pm to 4am.

During these months, thermal data were collected daily with a relatively even distribution

(Fig. 4).

Table 4. Percentage of sediment sieved from the mean high water mark (MHW), mid beach (MID) and toe of the beach (TOE) on Casey Key from 2004 to 2006 for seven sizes of particles, in both millimeters and phi size. From STCRP- unpublished data.

Beach Sieve size: mm, (phi size) Zone 4 (-2) 2 (-1) 1 (0) 0.5 (1) 0.25 (2) 0.125 (3) 0.063 (4) MHW 14.24% 17.95% 19.91% 15.34% 12.95% 18.38% 1.23% MID 10.87% 16.46% 19.65% 20.38% 16.16% 15.09% 1.40% TOE 2.78% 9.59% 20.64% 22.28% 25.36% 18.51% 0.85%

Temperature data were taken opportunistically for any adult female loggerhead sea turtle found emerging onto the nesting beach, climbing up the nesting beach, or in any part of the excavation process, as long as the eggs had not yet been covered. Data collection commenced after females began laying eggs, so as to avoid turtles abandoning their nesting effort. While this collection effort was not true random selection, it was an unbiased effort in that all females that were encountered were included.

Thermal data were collected in the 2008 season with an LT300 infrared (IR) thermometer (Sixth Sense) with an accuracy of ±1%. This thermometer was used to obtain surface temperatures from the water, waterline, and the beach sand, every three meters along the turtle crawl, all body pit attempts, the nest chamber, eggs laid in the nest chamber, and the surface of the gular skin of the nesting female. Temperatures were recorded within the crawl track created by the nesting female, and also one meter adjacent to the crawl track (from undisturbed sand). Temperature data were taken from

Month

Figure 3. Histogram of total data points collected by month for the 2008 and 2009 nesting seasons on Casey Key.

nest locations first, to ensure the female did not cover the nest before temperature data were taken, followed by readings from the water, then readings in sand locations every three meters following the crawl track of the turtle. Similar measurements were taken at corresponding locations one meter adjacent to the track to determine if thermal differences seen among locations within the track were due to turtle behavior or a

function of the thermal properties of the nesting beach. All readings for each crawling event were taken as quickly as possible (usually < 30 minutes), to obtain the most accurate thermal representation during the turtle’s emergence.

Day of the Week the of Day

Figure 4. Histogram of data points collected by day of the week for both the 2008 and 2009 nesting seasons on Casey Key.

Thermal measurements were repeated in the 2009 nesting season and augmented by an Omega HH11B Type K thermocouple probe (accuracy of ±0.1% of the reading, plus 1°C). The thermocouple probe was used for temperature readings at 2cm below the sand surface. Contrasting the two types of thermometers in tandem made it possible to determine if temperatures taken at sand surface and beneath the surface were significantly different. Temperatures at 2cm sand depth were represented based on observations by

Wood and Bjorndal (2000) that crawling loggerheads, through a thermally sensitive skin patch, “head plough” and expose their gular skin at 2cm depth, which may enable them to gauge beach characteristics.

Nests and False Crawls

Data were also recorded during nesting attempts that ended in a false crawl when possible. False crawl data were only taken if the turtle was seen on the beach, either approaching or leaving the beach. Fewer datasets were obtained from false crawls since tagging patrols inevitably invest more time with each nesting female.

Neophytes and Remigrants

The tagging effort on Casey Key that began in 1987 has yielded detailed individual nesting histories as well as clutches counted in each season. Turtles that did not have inconel flipper tags or tags scars were deemed neophytes, while turtles returning with attached tags from a previous season were remigrant turtles. Data were taken from neophytes and remigrant turtles. Data for serial nests laid by the same individual over the season gave insight on significant thermal variations among nests laid by the same

individual. Two case studies of individual turtles featured detailed data for turtles with detailed reproductive histories. A remigrant (Wiblet) laid 6 nests per season for three seasons (2004, 2005 and 2007) prior to data collection for this study. A neophyte

(Pepper) laid four nests within the 2008 season.

Environmental Parameters

I evaluated other environmental parameters with potential influence on nest site selection. Additional sand characteristics included sand coarseness (either sand or shell debris) and sand wetness (either wet or dry). Weather conditions during the nesting event were also recorded, including the presence or absence of rain, wind, or clouds. The vast majority (97.1%) of data were collected when it was not raining, while the remaining

2.9% were collected on rainy nights, without lightning. If lightning was present on or near the nesting beach, data collection ceased for safety reasons; however anecdotal observations are that turtles are less prone to emerge under lightning conditions. So this may be an unavoidable observer bias in my datasets. The majority (85.7%) of datasets were collected on calm nights, with the remaining 14.3% collected when air movement was clearly felt. Similarly, the majority (80.4%) of datasets were collected on nights with no cloud cover, while the remaining 19.6% of the data were collected on nights with at least some cloud cover. Beach slope was also taken at the same locations as the temperature readings, during the 2009 season only, using an angle locator.

Thermal Transect Data Collection

Additionally, comparative thermal transect data were obtained at four adjacent

Sarasota County beach segments that hosted comparable densities of nesting females:

Lido, South Siesta Key, North Casey Key, and North Venice. These data were collected opportunistically when females were not present, and used to compare to temperature data taken at the study site (south Casey Key), where females were present. These data were also used to determine the natural thermal variability in loggerhead nesting beaches near Casey Key. During the 2009 nesting season only, temperature data were taken from the four beaches using both the infrared thermometer and thermocouple probe. Slope data were taken using the angle locator and weather patterns, at the time data collection occurred, were recorded.

Rookery Contrasts

For further comparison, ancillary data were provided independently by collaborators at other loggerhead beaches from the Gulf of Mexico, Atlantic and Pacific

Basins to have a broader geographical scope of temperature data with which to compare to Casey Key thermal data. These loggerhead nesting beaches included Little

Cumberland Island, Georgia (1982 data by Dr. Tony Tucker), Wreck Island, Queensland,

Australia (2005 data by Dr. Tony Tucker), Keewaydin Island, Florida (2007 data by

David Addison of the Keewaydin Island Turtle Project), and Wassaw Island, Georgia

(2008, 2009 data by the Wassaw Caretta Research Project). Data were also available on

Casey Key in 2007 (data by Mote Marine Laboratory’s Sea Turtle Conservation and

Research Program), but like datasets from Little Cumberland Island, Wreck Island,

Keewaydin Island, and Wassaw Island, the data were taken by volunteers other than the researchers responsible for the 2008 and 2009 Casey Key data collection. Therefore, the methods used to collect the data from these other beaches may have differed from the methods set forth in this study.

Statistical Analysis

All descriptive and comparative statistics were performed with JMP software version 8 (Sall et al., 2001). In most cases, data were normally distributed (Fig. 5).

When data were normally distributed, t-tests, one-way ANOVAs, and fit models were used. These statistical tests allow considerable latitude, and deviations from normality are permissible under the central limit theorem (Byrkit, 1980). In addition, when sample sizes are large, parametric tests can be used (Byrkit, 1980). When data substantially deviated from normality, non-parametric tests were used, including Wilcoxon rank sum tests and Kruskal-Wallis tests.

Figure 5. Distribution of temperature data (using IR thermometer) within the crawl tracks of the adult female loggerhead turtles collected on Casey Key in 2008 and 2009 (n = 1462).

CHAPTER 3 – RESULTS

Correlation Between IR and Thermocouple Thermometers

The 2009 dataset compared a correlation of the temperatures collected with the infrared (IR) thermometer with those collected from the thermocouple probe. Surface temperature data from the IR thermometer and temperature data at 2cm depth from the thermocouple were highly correlated both within the crawl tracks and one meter adjacent to the crawl tracks (Fig. 6a; linear regression; adjusted R² = 0.677; p < 0.0001; n = 285;

Fig. 6b; linear regression; adjusted R² = 0.675; p < 0.0001; n = 281). Because there was a high correlation between IR thermometer and thermocouple temperature data on Casey

Key, and because the sample size of IR thermometer data was larger, only the IR thermometer data were used for the remainder of the study.

Thermal Comparison Between Nesting and False Crawling Females

2008 Nesting Season

There was a significant thermal difference between false crawl events and nesting events (Fig. 7; t-test; t = 2.67; p = 0.008; n = 883). Within the crawl, the mean temperature of the 6 false crawl events measured was 23.6°C ± 0.3°C, and the mean

(a)

(b)

temperature of the 88 nest events measured was 24.5°C ± 0.1°C (Table 5). One meter adjacent to the crawl there was no significant thermal difference between false crawl events and nesting events (t-test; t = 0.526; p = 0.599; n = 883). The mean sediment temperature adjacent to false crawl events was 23.5°C ± 0.3°C, and 23.7°C ±0.1°C adjacent to nest events (Table 5).

2009 Nesting Season

There was no significant thermal difference between false crawl events and nesting events, neither within the turtle crawl (t-test; t = -1.18; p = 0.24; n = 437), nor adjacent to the crawl (t-test; t = -1.35; p = 0.176; n = 433). Within the crawl, the mean temperature of the 2 false crawl events measured was 25.8°C ± 0.6°C and the mean temperature of the 57 nesting events measured was 25.0°C ± 0.1°C (Table 5). The mean sediment temperature adjacent to the false crawl events was 25.2°C ± 0.6°C, and 24.3°C

± 0.1°C adjacent to the nest events (Table 5).

Comparisons Between Seasons

There was a significant seasonal difference in the mean temperature of false crawl events within the crawl tracks (Wilcoxon test; Z = 3.19; p = 0.0014; n = 82). The mean temperature of false crawl events was 23.6°C ± 0.3°C in 2008 and 25.8°C ± 0.6°C in

2009 (Table 5). There was also a significant difference in the mean temperatures of false

Figure 6. Linear regressions comparing surface temperature data collected using an IR thermometer and temperature data collected at 2cm depth using a thermocouple probe (a) within the crawl tracks and (b) one meter adjacent to the crawl tracks, on Casey Key in 2009. Only locations with both an IR thermometer and thermocouple probe measurement were included in this test. The solid blue line indicates the least square line of fit (Celsius), and the dotted red lines indicate a 95% confidence interval about the line.

Figure 7. Box plot of a thermal comparison between false crawl and nesting events on Casey Key in 2008. Egg temperatures collected from nest events are excluded in this comparison.

crawl events between seasons one meter adjacent to the crawl tracks (t-test; t = 2.47; p =

0.015; n = 82). The mean temperature of the sediment adjacent to false crawl events was

23.5°C ± 0.3 in 2008 and 25.2°C ± 0.6 in 2009 (Table 5).

There was a significant seasonal difference in the mean temperatures from nesting events both within the crawl tracks and one meter adjacent to the crawl tracks (Fig. 8a; t- test; t = 3.29; p = 0.001; n = 1238; Fig. 8b; t-test; t = 4.35; p < 0.0001; n = 1234). The mean temperature of nesting events within the crawl tracks was 24.5 ± 0.1°C in 2008 and

25.0°C ± 0.1°C in 2009 (Table 5; egg temperatures excluded). Adjacent to the tracks, the

Table 5. Mean temperatures of all false crawl and nesting events measured on Casey Key in 2008 and 2009.

Temperature (°C ± standard error, °C) 2008 2009 Mean False Mean False Crawl Mean Nest Crawl Mean Nest Location Temperature Temperature Temperature Temperature

Within the Crawl 23.6 ± 0.3 24.5 ± 0.1 25.8 ± 0.6 25.0 ± 0.1 One Meter Adjacent to the Crawl 23.5 ± 0.3 23.7 ± 0.1 25.2 ± 0.6 24.3 ± 0.1

mean temperature of nesting events was 23.7°C ± 0.1°C in 2008 and 24.3°C ± 0.1°C in

2009 (Table 5). Egg temperatures and sediment temperatures one meter adjacent to the eggs were excluded in interannual comparisons of nesting events, so the same beach locations were used for each type of event (false crawl and nest) during seasonal comparison between both event types.

Thermal Comparison Among Nest Locations and Other Beach Locations

2008 Nesting Season

False Crawl Events

There was a significant thermal difference among locations on false crawl events

(Fig. A1; One-way ANOVA; F = 4.58; p < 0.0001; n = 68). A Tukey-Kramer post hoc test was conducted finding the mean temperatures of the water (W) and waterline (WL) were similar (p = 1.0) (Table 6, Table 7). The mean temperatures of wet sand (WS) and

(a)

(b)

dry sand (DS) were also thermally similar (Tukey-Kramer post hoc test; p = 0.996). The mean temperatures of W and WL were significantly different from WS and DS (Tukey-

Kramer post hoc tests; W/WS: p = 0.004; W/DS: p = 0.0003; WL/WS: p = 0.016;

WL/DS: p = 0.001). The remaining locations on false crawl tracks were thermally similar to all locations measured, including the apex of the false crawl (APEX), all body pit attempts (BP1, BP2, BP3), all nest chamber attempts (NC1, NC2), the spring high tide line (SHTL) and the dunes (DUNE) (Tukey-Kramer post hoc test).

Nest Events

There was a significant difference in the mean temperatures of different locations within the crawl tracks of nest events (Fig. A2; One-way ANOVA; F = 138.3; p <

0.0001; n = 901). A Tukey-Kramer post hoc test showed that the mean temperature of the two body pit attempts made closest to the water (BP3,BP4) were thermally similar to all locations measured on the tracks of nest events (Table 6; Table 7). The post hoc test also showed that many of the sediment locations leading up to the nest were thermally similar, including the body pit attempt made closest to the nest (BP2), wet sand (WS), dry sand (DS), damp sand (DAMP SAND), the high tide line (HTL), spring high tide line

(SHTL), and the dunes (DUNE) (Table 7).

Apart from body pit attempts BP3 and BP4, the mean temperature of the gular skin of the turtle (GULAR) was similar to the water (W), the body pit (BP1), and the nest chamber (NC1) (Table 7; Tukey-Kramer post hoc test). The body pit (BP1) was also

Figure 8. Box plots of thermal comparisons of all nesting events collected (a) within the crawl tracks and (b) one meter adjacent to the crawl tracks on Casey Key in 2008 and 2009. These figures exclude temperatures obtained from the eggs and sediment one meter adjacent to the eggs.

Table 6. List of all abbreviations for beach locations measured in the study and their meanings.

Beach Location Abbreviation Beach Location Definition Furthest point a female loggerhead crawled away from the water APEX before returning to the water; part of a false crawl event only Body pit location that was closest to the apex (false crawl event) or BP1 a part of the nest (nesting event) Body pit attempt was between BP1 and BP3 along the crawl track; BP2 attempt was closest to the apex or nest among all attempts Body pit attempt was in between BP2 and BP4 along the crawl BP3 track Body pit attempt nearest BP3; attempt was closest to the water BP4 among all attempts Sand surface was an intermediate moisture level between dry and DAMP SAND wet sand DS Sand surface was dry DS/SHELL Location was composed of both dry sand and shell debris DS/WRACK Location was composed of dry sand and wrack material DUNE Location was a part of a dune EGG Surface of an egg laid in the nest chamber GULAR Surface of the gular skin of the adult female loggerhead HTL High tide line Nest chamber that was nearest the apex (false crawl event) or the NC1 chamber that was a part of the nest (nesting event) Nest chamber attempt nearest NC1, but closer to the water than NC2 NC1 SHELL Location was composed of shell debris only SHELL/WRACK Location was composed of shell debris and wrack material SHTL Spring high tide line W Water WL Waterline Location was composed of wrack material only (vegetation WRACK primarily) Sand surface was wet (either recently washed over or exposed to WS rain) WS/SHELL Location was composed of wet sand and shell debris WS/WRACK Location was composed of wet sand and wrack material

Table 7. Mean temperatures of all locations measured within and one meter adjacent to the crawl tracks of both false crawl events and nest events on Casey Key in 2008. Subscripts indicate locations that were thermally similar (share the same letter) and significantly thermally different (do not share the same letter), for each column.

Temperature (°C) (± standard error, °C) False Crawl and False Crawl Events Nest Events Nest Events Within the crawl Within the crawl One meter adjacent Location tracks tracks to the tracks

APEX 23.6 ± 1.4 A, B * 23.9 ± 1.2 A, B

BP1 24.3 ± 1.0 A, B 26.5 ± 0.2 C 22.8 ± 0.2 B

BP2 24.6 ± 2.0 A, B 23.7 ± 0.5 D, E 23.1 ± 0.5 B

BP3 26.0 ± 2.0 A, B 23.8 ± 1.7 A, B, C, D, E 23.8 ± 1.2 A, B

BP4 * 23.6 ± 1.7 A, B, C, D, E 23.1 ± 1.7 A, B

DAMP SAND * 22.3 ± 0.7 E 22.8 ± 0.8 B

DS 22.2 ± 0.4 B 22.8 ± 0.1 E 22.8 ± 0.1 B

DUNE 23.5 ± 2.0 A, B 22.5 ± 0.7 D, E 22.5 ± 0.7 B

EGG * 29.2 ± 0.2 A 23.0 ± 0.2 B

GULAR * 26.4 ± 0.2 C 22.9 ± 0.2 B

HTL * 22.5 ± 0.8 D, E 22.5 ± 0.8 B

NC1 26.9 ± 2.0 A, B 28.6 ± 1.7 A, B, C, D 23.2 ± 1.2 A, B NC2 27.2 ± 2.0 A, B * 24.6 ± 1.7 A, B

SHTL 22.4 ± 2.0 A, B 23.1 ± 0.7 D, E 22.9 ± 0.7 B

W 26.8 ± 0.8 A 27.2 ± 0.2 B, C 27.0 ± 0.2 A

WL 26.4 ± 0.8 A 27.5 ± 0.2 B 27.3 ± 0.2 A WS 22.9 ± 0.4 B 22.6 ± 0.1 E 22.5 ± 0.1 B *Data were not collected for these locations in the 2008 season

thermally similar to the water (W) and nest chamber (NC1) (Tukey-Kramer post hoc test). Additionally, the nest chamber (NC1) was thermally similar to the water (W), waterline (WL), the body pit attempt made closest to the nest (BP2), the eggs, the high tide line (HTL), spring high tide line (SHTL), and dunes (DUNE) (Tukey-Kramer post hoc test). The only other location that was thermally similar to the eggs, besides BP3, and BP4, was the nest chamber (NC1) (Tukey-Kramer post hoc test).

Adjacent to the Crawl Tracks

There was a significant difference in mean temperatures of all locations measured one meter adjacent to the crawl tracks of false crawl and nesting events (Fig. A3; One- way ANOVA; F = 65.1; p < 0.0001; n = 969). A Tukey-Kramer post hoc test was conducted finding that most sediment locations adjacent to the tracks were thermally similar, including the sediment adjacent to the apex of the false crawls (APEX), body pit of the nest or attempt nearest the apex of the false crawls (BP1), all body pit attempts

(BP2, BP3, BP4), the nest chamber of the nest or attempt of a false crawl (NC1), nest chamber attempt (NC2), eggs (EGG), the turtle’s gular skin (GULAR), wet sand (WS), dry sand (DS), damp sand (DAMP SAND), high tide line (HTL), spring high tide line

(SHTL), and dunes (DUNE) (Table 6, Table 7). The post hoc test also revealed that the mean temperature of the water (W) and waterline (WL) were thermally similar to the

APEX, BP3, BP4, NC1, and NC2, but significantly different from the remaining locations, including BP1, BP2, EGG, GULAR, WS, DS, damp sand, HTL, SHTL and

DUNE (Table 7).

2009 Nesting Season

Within the Crawl Tracks

There was a significant difference in all locations measured within the crawl tracks of all false crawl and nesting events in the 2009 season (Fig. A4; One-way

ANOVA; F = 32.4; p < 0.0001; n = 491). A Tukey-Kramer post hoc test revealed that several locations on the turtle tracks were thermally similar to all locations measured, including the two body pit attempts made closest to the water (BP3, BP4), a nest chamber

attempt (NC2), and a location with a combination of dry sand and wrack material (DS/

WRACK) (Table 6; Table 8).

Many of the sediment locations leading up to the nest site were thermally similar, including wet sand (WS), damp sand, wrack material (WRACK), shell debris (SHELL), and sediment locations that were a combination of wet sand and wrack material (WS/

WRACK), dry sand and wrack material (DS/ WRACK), wet sand and shell debris (WS/

SHELL), dry sand and shell debris (DS/ SHELL), and shell debris and wrack material

(SHELL/ WRACK) (Table 8; Tukey-Kramer post hoc test). The mean temperature of dry sand (DS) was also thermally similar to these sediment locations, except wet sand

(WS) (Tukey-Kramer post hoc test; p < 0.0001), and shell debris (SHELL) (Tukey-

Kramer post hoc test; p = 0.0005).

In addition to BP3, BP4, NC2, and DS/WRACK, the gular skin of the turtles

(GULAR) was thermally similar to the water (W), waterline (WL), damp sand, the sediment that was a combination of wet sand and shell debris (WS/ SHELL), shell debris and wrack material (SHELL/ WRACK), the only other body pit attempt (BP2), the body pit of the nest or attempt nearest the apex of false crawls (BP1) and the nest chamber of the nest or attempt nearest the apex of the false crawls (NC1) (Table 8; Tukey-Kramer post hoc test). The body pit was thermally similar only to the locations that the turtle’s gular skin was similar to (Table 8). Location NC1 was thermally similar to all locations on the tracks, except the eggs (EGG) (Tukey-Kramer post hoc test; p = 0.01) and shell debris (SHELL) (Tukey-Krmaer post hoc test; p = 0.01). The eggs were significantly thermally different from all locations other than BP3, BP4, NC2, and DS/WRACK

(Table 8; Tukey-Kramer post hoc test).

Table 8. Mean temperatures of all locations measured within and one meter adjacent to the crawl tracks of both false crawl events and nest events on Casey Key in 2009. Subscripts indicate locations that were thermally similar (share the same letter) and significantly thermally different (do not share the same letter), for each column.

Temperature (°C) (± standard error, °C) False Crawl and Nest False Crawl and Nest Events Events One meter adjacent to Location Within the tracks the tracks

BP1 26.5 ± 0.2 B 24.0 ± 0.3 B, D

BP2 24.5 ± 0.6 B, C, D, E, F 24.2 ± 0.7 A, B, C, D

BP3 25.4 ± 1.2 A, B, C, D, E, F 25.3 ± 1.4 A, B, C, D

BP4 26.2 ± 1.7 A, B, C, D, E, F 25.8 ± 1.9 A, B, C, D

DAMP SAND 24.2 ± 0.8 B, C, D, E, F 24.2 ± 1.0 A, B, C, D DS 24.5 ± 0.2 C 24.5 ± 0.2 B

DS/SHELL 22.9 ± 1.0 C, D, E, F 23.0 ± 1.1 A, B, C, D

DS/WRACK 25.0 ±1.2 A, B, C, D, E, F 24.1 ± 1.4 A, B, C, D

EGG 28.5 ± 0.2 A 23.9 ± 0.3 B, D

GULAR 26.6 ± 0.2 B 23.8 ± 0.3 B, C, D

NC1 25.4 ± 0.7 B, C, D, E 23.8 ± 0.9 A, B, C, D

NC2 27.4 ± 1.7 A, B, C, D, E, F 26.3 ± 1.9 A, B, C, D

SHELL 21.5 ± 0.6 F 21.7 ± 0.7 C, D

SHELL/WRACK 23.6 ± 1.2 B, C, D, E, F 24.5 ± 1.4 A, B, C, D

W 26.5 ± 0.2 B 26.5 ± 0.3 A

WL 26.2 ± 0.2 B, D 26.1 ± 0.3 A

WRACK 22.8 ± 0.7 C, E, F 22.9 ± 0.9 B, C, D

WS 22.8 ± 0.2 E, F 22.7 ± 0.2 C

WS/SHELL 23.8 ± 1.2B, C, D, E, F 23.8 ± 1.4 A, B, C, D

WS/WRACK 22.7 ± 1.0 C, E, F 22.5 ± 1.1 A, B, C, D

Adjacent to the Crawl Tracks

There was a significant difference in all locations measured one meter adjacent to the tracks of both false crawl events and nest events (Fig. A5; One-way ANOVA; F =

11.8; p < 0.0001; n = 483). A Tukey-Kramer post hoc test was conducted finding that 11

of the 20 locations measured adjacent to the tracks of the turtles were thermally similar to all locations measured, including locations adjacent to all body pit attempts (BP2, BP3,

BP4), nest chamber attempt (NC2), nest chamber of the nest or an attempt in a false crawl event (NC1), damp sand, and locations that were a combination of wet sand and wrack material (WS/ WRACK), dry sand and wrack material (DS/ WRACK), wet sand and shell debris (WS/ SHELL), dry sand and shell debris (DS/ SHELL), and shell debris and wrack material (SHELL/ WRACK) (Table 6, Table 8). Apart from these locations, the water (W) and waterline (WL) were thermally similar (Tukey-Kramer post hoc test; p =

1.0), but significantly different from the remaining locations, including wet sand (WS), dry sand (DS), wrack material (WRACK), shell debris (SHELL), and sediment adjacent to the body pit of the nest or attempt in a false crawl event (BP1), eggs (EGG), and gular skin of the turtles (GULAR) (Table 8). Wet sand (WS) and shell debris were thermally similar (Tukey-Kramer post hoc test; p = 0.996) and significantly different from dry sand

(DS) (Tukey-Kramer post hoc test; WS, DS: p < 0.0001; SHELL, DS: p = 0.015).

Comparisons of Mean Temperatures Between the 2008 and 2009 Nesting Seasons

Mean Temperatures of the Sediment and Water

Within the Crawl Tracks

Only the mean temperatures of the water, waterline, dry and wet sand were used for seasonal comparisons. Between the two seasons, no significant differences were observed in mean water or waterline temperatures within the tracks of false crawl events

(Table 9; W: Wilcoxon rank sum test; Z = 0.129; p = 0.896; n = 9; WL: Wilcoxon rank

Table 9. Mean water and sand temperatures measured within and one meter adjacent to the crawl tracks of false crawl and nest events, including p-values of relevant statistical tests conducted between the 2008 and 2009 nesting seasons on Casey Key.

Temperature (°C) Temperature (°C) (± standard error, °C) p-value p-value (± standard error, °C) p-value False Crawl False Crawl and Nest False Crawl and Nest Events Nest Events Events Events Nest Events One meter Within the One meter adjacent to the adjacent to the Within the tracks tracks Within the tracks tracks tracks Wilcoxon rank t-test between sum test between t-test between Location 2008 2009 seasons seasons 2008 2009 seasons

39 Water 27.2 ± 0.1 26.5 ± 0.2 0.0003 0.896 27.0 ± 0.1 26.5 ± 0.2 0.007

Waterline 27.5 ± 0.2 26.2 ± 0.2 <0.0001 0.518 27.3 ± 0.2 26.1 ± 0.2 0.0001 Dry sand 22.8 ± 0.1 24.5 ± 0.2 <0.0001 * 22.8 ± 0.1 24.5 ± 0.2 <0.0001 Wet sand 22.6 ± 0.1 22.7 ± 0.2 0.779 0.027 22.5 ± 0.1 22.7 ± 0.2 0.523 *Dry sand temperatures were not collected on false crawl tracks in the 2009 season.

sum test; Z = -0.645; p = 0.518; n = 9). However, mean wet sand temperatures were significantly different within the false crawl tracks between the two seasons (Table 9;

Wilcoxon rank sum test; Z = 2.21; p = 0.027; n = 25).

For nest events, there was a significant difference in the mean temperature of the water (W), waterline (WL) and dry sand (DS) within the crawl tracks (Table 9; W: Fig. 9; t-test; t = -3.68; p = 0.0003; n = 144; WL: Fig. 10; t-test; t = -4.52; p < 0.0001; n = 143;

DS: Fig. 11; t = 7.35; p < 0.0001; n = 267). The mean wet sand temperature was not significantly different among seasons for nest events (Table 9; t-test; t = 0.279; p = 0.779; n = 325).

Figure 9. Box plot of the mean water temperatures within the crawl tracks of nest events on Casey Key in 2008 and 2009.

Figure 10. Box plot of the mean waterline temperatures within the crawl tracks of nest events on Casey Key in 2008 and 2009.

Adjacent to the Crawl Tracks

The mean temperature of the water (W), waterline (WL) and dry sand (DS) were significantly different among the two seasons for false crawl and nesting events (Table 9;

W: Fig. 12; t-test; t = -2.71; p = 0.007; n = 153; WL: Fig. 13; t-test; t = -3.92; p = 0.0001; n = 152; DS: Fig. 14; t-test; t = 7.34; p < 0.0001; n = 290). The mean temperature of wet sand was not significantly different among the two seasons (Table 9; t-test; t = 0.639; p =

0.523; n = 350).

Figure 11. Box plot of the mean dry sand temperatures within the crawl tracks of nest events on Casey Key in 2008 and 2009.

Mean Temperatures of the Nest Site

Within the Crawl Tracks

The mean temperature of the eggs was the only mean temperature that was significantly different among seasons (Fig. 15; t-test; t = -3.18; p = 0.002; n = 140). All other mean temperatures within the nest site, including the body pit (BP1), nest chamber

(NC1) and the gular skin of the turtles (GULAR), were not significantly different among the two seasons (Table 10; BP1: t-test; t = 0.059; p = 0.953; n = 140; NC1: Wilcoxon rank sum test; Z = 1.06; p = 0.289; n = 5; GULAR: t-test; t = 0.619; p = 0.537; n = 141).

Figure 12. Box plot of the mean water temperature one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2008 and 2009.

Adjacent to the Crawl Tracks

Mean temperatures of the sediment adjacent to the body pit (BP1), eggs (EGG), and the nesting female (GULAR) were significantly different among the two seasons

(Table 10; BP1: Fig. 16; t-test; t = 4.17; p < 0.0001; n = 137; EGG: Fig. 17; t-test; t =

2.88; p = 0.005; n = 136; GULAR: Fig. 18; t-test; t = 3.15; p = 0.002; n = 139). The mean temperature of the sediment adjacent to the nest chamber was not significantly different among seasons (Table 10; Wilcoxon rank sum test; Z = -0.354; p = 0.724; n =

5).

Figure 13. Box plot of the mean waterline temperature one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2008 and 2009.

Effect of Weather on Mean Temperatures of the Sediment and Nest Site

2008 Nesting Season

Within the Crawl Tracks

Rain. The locations used for weather comparisons included water, waterline, wet sand, dry sand, body pit (nests only), nest chamber (nests only), and the gular skin of the turtles (nests only). The mean temperatures of wet sand (WS), dry sand (DS) and the gular skin of the turtles (GULAR) within the tracks of nest events were all significantly

Figure 14. Box plot of the mean dry sand temperature one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2008 and 2009.

different in rainy and non-rainy conditions (WS, DS combined: Fig. 19; t-test; t = 2.57; p

= 0.01; n = 432; GULAR: Fig. 20; t-test; t = 2.18; p = 0.032; n = 86). The mean temperature of the water (W) and waterline (WL) were not significantly different in rainy and non-rainy conditions within the tracks of nest events (W, WL combined: fit model; t

= -1.72; p = 0.088; n = 177). The mean temperatures of the body pit (BP1), nest chamber

(NC1) and eggs (EGG) were also not significantly different (BP1, NC1combined: fit model; t = 0.13; p = 0.896; n = 87; EGG: fit model; t = 1.58; p = 0.119; n = 86). The mean temperatures of the water, waterline, wet sand, and dry sand for false crawl events were not analyzed because there was not sufficient presence/absence data.

Figure 15. Box plot of the mean temperature of the surface of the eggs laid in nests on Casey Key in 2008 and 2009.

Cloud Cover. There was a significant difference in the mean temperatures of wet sand (WS) and dry sand (DS) for false crawl events between cloudy and clear conditions

(WS, DS combined: Fig. 21; t-test; t = 4.1; p = 0.0002; n = 44). The mean temperature of wet sand (WS) and dry sand (DS) within the crawl tracks of nesting events were not significantly different between the two conditions (WS, DS combined: fit model; t = -

1.92; p = 0.056; n = 432). There was also no significant difference in mean temperatures of the water (W) and waterline (WL) for false crawl events or nest events between the two conditions (W, WL combined: false crawls: Wilcoxon rank sum test; Z = 0.08; p =

0.936; n = 12; nest events: fit model; t = -0.31; p = 0.755; n = 177). Additionally, there were no significant differences in mean temperatures of the body pit (BP1), nest chamber

Table 10. Mean temperatures within and one meter adjacent to the nest site and p-values of relevant statistical tests conducted between the 2008 and 2009 nesting seasons on Casey Key.

Temperature (°C) Temperature (°C) (± standard error, °C) p-value (± standard error, °C) p-value Nest Temperatures t-test Sediment Temperatures t-test Within the nest between Adjacent to the nest between Location 2008 2009 seasons 2008 2009 seasons Body pit 26.5 ± 0.2 26.5 ± 0.2 0.953 22.7 ± 0.2 24.0 ± 0.3 <0.0001 Nest chamber – – 0.289* – – 0.724* Eggs 29.2 ± 0.2 28.5 ± 0.2 0.002 23.0 ± 0.2 23.9 ± 0.3 0.005 Gular skin of turtles 26.4 ± 0.1 26.6 ± 0.2 0.537 22.9 ± 0.2 23.8 ± 0.3 0.003 *This p-value was obtained via a Wilcoxon rank sum test, not a t-test.

Figure 16. Box plot of the mean temperature of the sediment one meter adjacent to the body pit of nests on Casey Key in 2008 and 2009.

(NC1), eggs (EGG) or gular skin of the turtles (GULAR) between the two conditions

(BP1, NC1 combined: fit model; t = -1.13; p = 0.262; n = 87; EGG: fit model; t = -0.70; p

= 0.486; n = 86; GULAR: fit model; t = 0.81; p = 0.422; n = 86).

Wind. There was not sufficient presence/absence data to analyze mean temperature differences for false crawls. Among the locations with sufficient data for nest events, including water (W), waterline (WL), wet sand (WS), dry sand (DS), body pit (BP1), nest chamber (NC1), eggs (EGG), and the gular skin of the turtles (GULAR), there were no significant differences in mean temperatures between windy and calm conditions (W, WL combined: fit model; t = 0.65; p = 0.517; n = 177; WS, DS combined:

Figure 17. Box plot of the mean temperature of the sediment one meter adjacent to the eggs laid in nests on Casey Key in 2008 and 2009.

fit model; t = 0.08; p = 0.934; n = 432; BP1, NC1 combined: fit model; t = -0.22; p =

0.827; n = 87; EGG: fit model; t = 0.81; p = 0.419; n = 86; GULAR: fit model; t = -0.10; p = 0.919; n = 86).

Adjacent to the Crawl Tracks

Rain. There was a significant difference in the mean temperatures of wet sand

(WS) and dry sand (DS) between rainy and non-rainy conditions, adjacent to false crawl and nest events combined (WS, DS combined: Fig. 22; t-test; t = 2.69; p = 0.0073; n =

476). There was also a significant difference in the mean temperature of sediment

Figure 18. Box plot of the mean temperature of the sediment one meter adjacent to the gular skin of the nesting females on Casey Key in 2008 and 2009.

adjacent to the body pit (BP1), nest chamber (NC1), eggs (EGG), and the gular skin of the turtles (GULAR) for nest events between the two conditions (BP1, NC1, EGG and

GULAR combined: Fig. 23; t-test; t = 3.38; p = 0.0008; n = 259). The mean temperature of the water (W) and waterline (WL) adjacent to the tracks was not significantly different between the two conditions for false crawl and nest events combined (W, WL combined: fit model; t = -1.92; p = 0.057; n = 189).

Cloud Cover. There was a significant difference in mean wet sand (WS) and dry sand (DS) temperatures between cloudy and clear conditions for false crawl and nest events combined (WS, DS combined: Fig. 24; t-test; t = 2.2; p = 0.028; n = 476). There

Figure 19. Box plot of the mean temperatures of wet and dry sand (combined within each condition, N and Y) within the crawl tracks of nesting events according to the absence (N) and presence (Y) of rain on Casey Key in 2008.

was no significant difference in the mean temperatures of water (W) and waterline (WL) between the two conditions for false crawl and nest events combined (W, WL combined: fit model; t = -0.59; p = 0.553; n = 189). Nor was there a significant difference in mean temperatures of the sediment adjacent to the body pit (BP1), nest chamber (NC1), eggs

(EGG), or gular skin of the turtles (GULAR) between the cloudy and clear conditions for nest events (BP1, NC1, EGG and GULAR combined: fit model; t = -1.17; p = 0.245; n =

259).

Wind. There were no significant differences in the mean temperatures of the water (W), waterline (WL), wet sand (WS), or dry sand (DS) between windy and calm

Figure 20. Box plot of the mean temperature of the surface of the gular skin of nesting females in the absence (N) and presence (Y) of rain on Casey Key in 2008.

conditions for both false crawl and nest events combined (W, WL combined: fit model; t

= -0.02; p = 0.988; n = 189; WS, DS combined: fit model; t = 0.17; p = 0.864; n = 476).

Nor was there a significant difference in mean temperatures of the sediment adjacent to the body pit (BP1), nest chamber (NC1), eggs (EGG), or gular skin of the turtles

(GULAR) between the two conditions for nest events (BP1, NC1, EGG and GULAR combined: fit model; t = 0.53; p = 0.596; n = 259).

Figure 21. Box plot of the mean temperature of wet and dry sand (combined within each condition, N and Y) within the crawl tracks of false crawl events according to the absence (N) and presence (Y) of cloud cover on Casey Key in 2008.

2009 Nesting Season

Within the Crawl Tracks

Rain. There were no data collected in the presence of rain this season, therefore no analyses were undertaken for this parameter.

Cloud Cover. The mean dry sand temperature was significantly different in cloudy and clear conditions for nest events (Wilcoxon rank sum test; Z = -2.25; p =

0.025; n = 72). The mean temperature of eggs was significantly different between the two conditions within the crawl tracks of nest events (Wilcoxon rank sum test; Z = -2.4; p

= 0.016; n = 54). The mean temperatures of the water (W), waterline (WL), and wet sand

(WS) were not significantly different between cloudy and clear conditions for false crawl

Figure 22. Box plot of the mean temperature of wet and dry sand (combined within each condition, N and Y) one meter adjacent to the crawl tracks of false crawl and nesting events in the absence (N) and presence (Y) of rain on Casey Key in 2008.

and nesting events combined (W,WL combined: fit model; t = 0.37; p = 0.715; n = 116;

WS: Wilcoxon rank sum test; Z = -0.046; p = 0.963; n = 92). The mean temperatures of the body pit (BP1), nest chamber (NC1) and gular skin of the turtles (GULAR) for nest events were not significantly different between the two conditions (BP1, NC1combined:

Wilcoxon rank sum test; Z = -1.61; p = 0.108; n = 58; GULAR: fit model; t = 0.83; p =

0.411; n = 55).

Wind. The mean temperatures of the body pit (BP1), nest chamber (NC1) and eggs (EGG) for nest events were significantly different between windy and calm conditions (BP1, NC1 combined: Wilcoxon rank sum test. Z = -2.49; p = 0.013; n = 58;

Figure 23. Box plot of the mean temperature of the sediment one meter adjacent to the body pit, nest chamber, eggs, and gular skin of the female (combined within each condition, N and Y) for nesting events in the absence (N) and presence (Y) of rain on Casey Key in 2008.

EGG: Wilcoxon rank sum test; Z = -2.3; p = 0.021; n = 54). The mean dry sand temperature for nest events was not significantly different between the two conditions

(Wilcoxon rank sum test; Z = -1.76; p = 0.079; n = 72). The mean temperatures of the water (W), waterline (WL) and wet sand (WS) for false crawl and nest events were also not significantly different between windy and calm conditions (W, WL combined: fit model; t = 1.08; p = 0.281; n = 116; WS: Wilcoxon rank sum test; Z = -0.665; p = 0.506; n = 92). Additionally, the mean temperature of the gular skin of the turtles for nesting events was not significantly different between the two conditions (fit model; t = 0.94; p =

0.354; n = 55).

Figure 24. Box plot of the mean temperature of wet and dry sand (combined within each condition, N and Y) one meter adjacent to the crawl tracks of both false crawl and nesting events in the absence (N) and presence (Y) of cloud cover on Casey Key in 2008.

Adjacent to the Crawl Tracks

Cloud Cover. The mean dry sand temperatures adjacent to nest events were significantly different between cloudy and clear conditions (Wilcoxon rank sum test; Z =

-2.56; p = 0.01; n = 71). The mean temperatures of the sediment adjacent to the body pit

(BP1), nest chamber (NC1), eggs (EGG) and gular skin of the turtles (GULAR) were also significantly different between the two conditions (BP1, NC1, EGG, GULAR combined:

Wilcoxon rank sum test; Z = -2.07; p = 0.039; n = 160). The mean temperatures of the water (W), waterline (WL) and wet sand (WS) adjacent to false crawl and nest events were not significantly different between cloudy and clear conditions (W, WL combined:

fit model; t = 0.41; p = 0.684; n = 116; WS: Wilcoxon rank sum test; Z = -0.585; p =

0.556; n = 92).

Wind. The mean dry sand temperature for nest events was not significantly different between windy and calm conditions (Wilcoxon rank sum test; Z = -1.88; p =

0.059; n = 71). The mean temperatures of the sediment adjacent to the body pit (BP1), nest chamber (NC1), eggs (EGG) and gular skin of the turtles (GULAR) were also not significantly different between the two conditions (BP1, NC1, EGG, and GULAR combined: Wilcoxon rank sum test; Z = -1.65; p = 0.098; n = 160). Furthermore, the mean temperatures of the water (W), waterline (WL) and wet sand (WS) for false crawl and nest events were also not significantly different between windy and calm conditions

(W, WL combined: fit model; t = 0.92; p = 0.36; n = 116; WS: Wilcoxon rank sum test; Z

= -0.464; p = 0.643; n = 92).

Correlation Between Beach Slope and Distance

On average, the beach width and beach slope were negatively correlated when taken independently of the turtle tracks (Spearman rank correlation; ρ = -0.354; p = 0.05; n = 31). In contrast, the crawl distance and beach slope was positively correlated

(Spearman rank correlation; ρ = 0.3003; p = 0.05; n = 43).

CHAPTER FOUR – DISCUSSION

IR vs. Thermocouple Comparisons

In the data collected from Casey Key in the 2008 and 2009 nesting seasons, there was a strong correlation of temperatures obtained with an IR thermometer and thermocouple, both within the crawl tracks and one meter adjacent to them (Fig. 6a, Fig.

6b). The efficacy of an IR thermometer was also demonstrated by Rowley and Alford

(2007), who found that cloacal temperatures of tree frogs (Litoria caerulea) were better predicted by surface temperatures measured by an IR thermometer than it was by using a thermocouple.

However, the regressions in the present study explained only about 67% of the variation in temperature readings, which may be attributed to a host of factors, including differences in accuracy of the devices themselves or failure to equilibrate the instrument.

Additionally, orientation of the IR thermometer may be important when recording temperature, as Hare et al. (2007) showed that the influence of background temperature was substantial if the IR thermometer was oriented 90° to the body of small skinks. My study of Casey Key sand properties measured background temperatures only, but it nevertheless shows that interference is possible when using an IR thermometer. Because the IR thermometer is fast, easy to use, convenient and comparable to a thermocouple

thermometer, an IR thermometer remains a viable option for subsequent thermal studies on nesting beaches. To the best of my knowledge, this is the first study to show the efficacy of IR thermometers in the treatment of loggerhead sea turtles in the field.

Thermal Relationships: 2008 and 2009 on Casey Key

In two nesting seasons, there was a fundamental thermal relationship maintained between the nesting female and the nesting beach: the body pit within the nest (BP1) was nearly identical to the surface of the gular skin of the nesting female (GULAR). A difference between the mean temperature of BP1 and GULAR in both seasons was

±0.1°C (Table 10). Additionally, the mean temperature of BP1 in both seasons was consistent, 26.5°C ± 0.2 (Table 10).

These results may suggest that females associate with a thermal location on the nesting beach similar to their own skin as a guide to locate a suitable nest site. According to Miller et al. (2003), successful incubation temperatures for loggerhead sea turtles range from 25°C to 34°C in the eastern United States. The mean temperatures of the gular skin of the turtles, the body pit, and nest chamber were all within range for successful incubation (Table 10). Female turtles may use their own temperature as a proxy for successful incubation on land because the eggs are already being successfully incubated at that temperature. As ectotherms, sea turtles regulate their body temperature by exchanging heat with the environment. Turtles operate in a marine environment the majority of their lives. Water has a high heat capacity and high thermal conductivity so it acts as a temperature stabilizer (Spotila et al., 1997). Loggerheads maintain a small (1-

2°C) temperature difference between the body core and the water; therefore they may utilize their body temperature as a reliable cue while operating in an unfamiliar terrestrial environment. In addition, it is possible that the similarity in temperatures between the nest site and the female avoids metabolic alterations in the embryos due to drastic changes of temperature (Ackerman, 1997; López-Castro et al., 2004).

While this study did not assess the sex ratios of males and females hatched in nests on Casey Key, the relationships among nesting beach temperature and nest site selection and the consequences for sex ratio should be assessed in a future study. The degree to which temperature is used in nest site selection each nesting season may relate to the sex ratios of hatchlings because environmental factors can influence embryo survivorship, hatchling quality and sex ratio (Wood and Bjorndal, 2000).

The results of my study do not concur that the turtles are searching for an abrupt change in temperature, as suggested by Stoneburner and Richardson (1981), but rather that females use thermal cues as a part of the decision making process. This finding is also in direct contrast to Hays et al. (1995) that suggested turtles traveled a random distance above the most recent high water line and Mrosovsky (1983) that suggested nesting turtles adopt a scatter nesting strategy to ensure that at least some nests will be appropriately sited (Table 1). In fact, the results of the present study show no indication that they seek out the high tide line, as the gular skin of the female was not thermally similar to the high tide line on Casey Key in the 2008 nesting season. The high tide line and spring high tide line were, however, thermally similar to all body pit attempts (BP2,

BP3, BP4) in the 2008 season (Table 7; Fig. A2). This may suggest that the females utilize environmental parameters other than the location of the high tide line.

In both the 2008 and 2009 seasons, the mean temperature of the surface of the gular skin of the female (GULAR) was similar to the body pit attempts closest to the water (BP3, BP4), yet the female chose not to nest at these locations (Table 7; Table 8;

Fig. A2; Fig. A4). Additionally, during the 2008 season the mean temperature of the body pit attempt made closest to the nest (BP2) was significantly different from the mean temperature of the gular skin of the female (GULAR) (Table 7; Fig. 25). These results may suggest that other environmental factors may be integrated into their decision. If gravid females considered thermal cues only in the nest site selection process, they would nest at the first location they encountered that was thermally similar to their own skin.

Because these turtles did not nest at body pit attempt BP4 (the first body pit turtles constructed), suggests that more information is included in the decision of nest site location. Additionally, other environmental factors may override the importance of thermal similarity between the female and nest site if turtles were willing to attempt to nest in a location (BP2) that was not thermally similar to them in the 2008 season (Table

7). The relative importance of each environmental parameter should be considered in a future study.

In both the 2008 and 2009 seasons, the mean temperatures of most sediment locations leading up to the nest site were thermally similar. These locations included dry sand (DS), wet sand (WS), damp sand, the high tide line (HTL), spring high tide line

(SHTL) and dunes (DUNE) in the 2008 season (Fig. 26). In the 2009 season, wet sand

(WS), damp sand, wrack material (WRACK), shell debris (SHELL), and many locations with a combination of sediment and/or vegetation, such as wet sand and wrack material

(WS/WRACK), dry sand and wrack material (DS/WRACK), wet sand and shell debris

Figure 25. Box plot of the mean temperatures of the body pit attempt made closest to the nest site (BP2) and the gular skin of the turtle (GULAR) within the crawl tracks of nest events on Casey Key in 2008.

(WS/SHELL), dry sand and shell debris (DS/SHELL), and shell debris and wrack material (SHELL/WRACK) (Fig. 27). The thermal similarity of locations along a crawl track suggests that there may be few significant thermal differences across a beach transect for females to discriminate. Thus, a female may detect a similar thermal cue that matches her gular skin to nest because there are few reliable temperature differences on the nesting beach to guide her to that location, when most substrates on Casey Key were all thermally similar. This finding allows that other environmental parameters may be integrated into the decision making process. Other studies have suggested that warm air temperature and water temperature may be related to nesting phenology (Table 1; Bowen

Figure 26. Box plot of the mean temperatures of the sediment and water within the crawl tracks of nest events on Casey Key in 2008.

et al., 2005; Pike, 2008), although that differs in scale from nest site selection.

The importance of temperature to the gravid female may vary among nesting seasons as well. There were significant inter-season differences in the mean temperature of wet sand within the crawl tracks of false crawl events and the mean temperatures of the water (Fig. 9), waterline (Fig. 10), and dry sand (Fig. 11) within the crawl tracks of nest events. Similarly, there were inter-season differences one meter adjacent to the crawl tracks of false crawl and nest events in the mean temperatures of the water

Figure 27. Box plot of the mean temperatures of the sediment and water within the crawl tracks of both false crawl and nest events on Casey Key in 2009.

(Fig. 12), waterline (Fig. 13), and dry sand (Fig 14). There were inter-season differences in the sediment one meter adjacent to the body pit of the nest site (Fig. 16), the eggs (Fig.

17), and the gular skin of the female (Fig. 18) of nest events only. Additionally, the mean temperatures of false crawls and nesting events were significantly different in the 2008 nesting season (Fig. 7), but similar in the 2009 nesting season. In summary, thermal variation within and across seasons is to be expected. In light of this, temperature may be

a more important cue in some years than others. Future studies will want to determine the primacy of thermal cues, if for example turtles continually search for a temperature on the beach similar to their own or when temperature is abandoned and secondary environmental parameters are employed to locate a nest site.

A critical observation of my study might question whether thermal artifacts of a nesting female are transferring heat to the sediment since my thermal measurements were taken after she had begun laying eggs. My study did not quantify this potential heat transfer, or how quickly the females acclimated to terrestrial temperatures, but these factors should be considered in future studies. Heat transfer from the turtle to the sediment may be important if it influences the turtle’s gular skin, yielding an inaccurate temperature from the thermometer. However, sea turtles have a large thermal inertia and seldom equilibrate with environmental conditions (Spotila et al., 2003). Instead, their body temperature approaches the environmental temperature over several hours or days

(Spotila et al., 2003). Because most turtles observed in the present study were not on the nesting beach for more than an hour, the degree to which their behavior was augmented by the environmental temperature may not have been significant. In any case, these potential artifacts cannot be avoided in a field study because the turtle may abandon the nesting attempt if she is approached before she begins laying eggs.

Weather and Temperature Relationships: 2008 and 2009

In the 2008 nesting season, rain yielded the most significant temperature differences. The mean temperatures of wet sand, dry sand and the gular skin of the

females within the crawl tracks of nesting events were all affected by rain conditions

(Fig. 19; Fig. 20). Additionally, the mean temperatures of wet and dry sand adjacent to both false crawl and nesting events were modified by rain (Fig. 22). Furthermore, the sediment adjacent to the body pit, nest chamber, eggs, and the gular skin of the turtles one meter adjacent to the crawl tracks of nesting events were significantly different according to rain (Fig. 23). Mean temperature differences in relation to rain could not be assessed in the 2009 season because a safe opportunity to obtain data in rainy conditions did not present itself. Some mean temperatures showed a significant difference according to cloud cover as well. The mean temperatures of wet and dry sand within the crawl tracks of false crawl events and one meter adjacent to the tracks of false crawl and nest events were significantly different according to cloud cover (Fig. 21; Fig. 24). In each of these cases, at least in the 2008 season, the mean temperatures in the presence of these conditions were all significantly warmer than in the absence of these conditions, which suggests that rain and cloud cover may serve to retain heat onto the nesting beach.

In the 2009 nesting season, cloud cover yielded the most significant temperature differences: dry sand within and one meter adjacent to the crawl tracks of false crawl and nesting events, mean egg temperatures within the nest, and the sediment adjacent to body pit, nest chamber, eggs and gular skin of the turtles. Finally, the mean temperatures of the body pit, nest chamber, and eggs within the crawl tracks of nest events were the only mean temperatures that were significantly different between windy and calm conditions in the 2009 season.

One study has associated rainfall with the number of nests laid by female loggerheads within a nesting season, along with moderate tidal cycles (Table 1; Pike,

2008). Other studies have also hypothesized that rainfall is an important factor that signals different species of turtles to nest (Table 1; Burke et al., 1994; Wilson et al., 1999;

Bowen et al., 2005). Successful nesting, however, has been related to higher barometric pressure (Table 1; Pike 2008). Additionally, the degree to which a nesting beach is exposed to wind seemed to have an influence on the spatial distribution of nest sites and perhaps nest site selection in female sea turtles (Table 1; Garcon et al., 2010). Olive ridley turtles tend to nest on windy and cloudy days when there is less heating due to solar radiation (Table 1; Spotila et al., 2003). While these studies evaluated the potential effects of weather conditions on the number of nests laid or nest site selection, to my knowledge there seems to be no other published studies on how weather affects temperature of the beach and how that may affect nest site selection. While mean temperature differences were seen according to these various weather conditions, it cannot be stated for certain if these weather conditions were the cause of these significant temperature differences, and if these weather conditions resulted in the behavior seen in loggerhead turtles nesting on Casey Key. Definitive causes of significant temperature differences cannot be determined in a descriptive study such as this study as it does not allow environmental manipulation or control.

Slope as a Cue for Nest Site Selection

There was a significant negative correlation between beach width and beach slope in the 2009 loggerhead nesting season on Casey Key. In contrast, there was a significant positive correlation between beach width and beach slope along the upcrawl of the turtle

track. These findings may suggest that Casey Key becomes increasingly flat from water to duneline, but female loggerheads seek out a location of greatest incline, which may offer drainage protection from inundation damage in high tides or storm activity. While these correlations are significant, they are not strong correlations. Distance only explains

35 percent of the variation in slope of the undisturbed beach and 30 percent of the variation in slope of the turtle upcrawls, which may mean that there are other environmental parameters that explain the variation in slope other than distance.

Therefore, if turtles are using slope as a cue to locate a nest site, they are integrating more cues than just the distance they travel to make a decision on slope. It may be that females use ambient light from the landward horizon to determine slope as well, which should be considered in a future study.

My finding agrees with Wood and Bjorndal (2000) that slope may be a cue that females use to locate a suitable nest site (Table 2). While Wood and Bjorndal (2000) suggested slope is the most important factor, our study cannot make that claim, only that slope may be a cue used by the females. This study also agrees with Horrocks and Scott

(1991), Blamires et al. (2003), Spanier (2010), who also suggest that slope may be a contributing factor to nest site selection (Table 2).

The influence slope has on nest site selection may be a function of the energy a nesting beach is exposed to, which can vary significantly between beaches exposed to the

Atlantic Ocean and the Gulf of Mexico. The Archie Carr National Wildlife Refuge, a

Florida Atlantic coast beach, is characterized as a high energy beach with a sloped berm and a steeply scarped foredune (Wood and Bjorndal, 2000). In the Wood and Bjorndal

(2000) study, beach slope increased significantly near the waterline, remained constant at

midbeach, and increased significantly near nests. Casey Key, on Florida’s west coast, is a comparatively low energy beach. Aside from the ephemeral scarps after a severe weather or tidal event, Casey Key experiences relatively weak wave energy, allowing for relatively flat beach profiles with low, rolling foredunes. Florida’s limestone continental shelf extends approximately 250km from Casey Key, dampening wave energy and protecting Casey Key from severe wave activity. The shelf only extends approximately

50km from the Archie Carr National Wildlife Refuge, exposing the beach to surface gravity waves of the Atlantic, and producing a relatively steep, severe coastline. Thus, wave energy may indirectly affect loggerhead nest site selection in Florida by way of beach topography. Wave energy shapes the beach profile, and turtles use the features of that profile to select a nest site.

Slope may be a more important cue for turtles nesting on the Archie Carr National

Wildlife Refuge because it is a prominent feature of the beach. Slope may be less influential to turtles nesting on Casey Key as it is not a pronounced feature, leaving turtles to utilize other environmental parameters, such as temperature, to make the most effective decision. This comparison shows that the coastline turtles nest upon needs to be critically considered in a nest site selection study, as environmental parameters can be used by turtles in significantly different ways, and to significantly different degrees.

Case Study 1: Serial Measurements of a Remigrant Loggerhead

Thermal Relationships

Wiblet is a remigrant female loggerhead that was sampled a total of six times: three nest events in 2008 and two nest events and one false crawl event in 2009. Wiblet has a reproductive history on Casey Key in the 2002, 2003, 2004, 2005, 2007, 2008, 2009 and 2011 seasons.

In 2008 there was a significant difference in the mean temperatures of locations within the crawl tracks of her nest events (Fig. A6; One-way ANOVA; F = 7.617; p =

0.0002; n = 27). A Tukey-Kramer post hoc test was conducted finding thermal measurements similar to Wiblet’s gular skin included the water (p = 0.999), waterline (p

= 0.999), wet sand (p = 0.275), body pit (p = 0.999) and eggs (p = 1.0). These repeated data for an individual suggest a strong thermal association between her gular skin and nest site selection.

In 2009 there was an insignificant thermal difference between false crawls and nests (Wilcoxon rank sum test; Z = 1.89; p = 0.059; n = 20). Additionally, there was no significant thermal difference in mean temperatures of any locations measured within the crawls of Wiblet’s nest events (Kruskal-Wallis test; H = 8.35; 8 d.f.; p = 0.40; n = 16), nor any significant thermal difference within the crawls of false crawls (Kruskal-Wallis test; H = 2.70; 2 d.f.; p = 0.259; n = 4). While the turtle may have chosen to nest in a location thermally similar to her own temperature (because all locations within the crawl track were similar, including locations within the nest site), it seems implausible for the turtle to discriminate thermally between locations within its path for each type of event.

Additionally, it appears unlikely the turtle used temperature as a sole cue to decide whether to false crawl or nest and was selecting nest sites based on a suite of cues, which still happen to include thermal properties.

Between seasons, there was a significant difference among mean temperatures within the crawl tracks of nest events and one meter adjacent to the tracks (within the tracks: Fig. 28; t-test; t = -3.16; p = 0.003; n = 43; one meter adjacent: Fig. 29; t-test; t = -

2.25; p = 0.03; n = 43). Mean temperatures encountered by Wiblet in the 2009 season were significantly cooler than those encountered in the 2008 season. The mean temperature of nest events in the 2008 season was 26.7°C ± 0.5°C, while in the mean temperature in the 2009 season was 24.3° ± 0.6°C. The mean temperature of water and sediment adjacent to the tracks was 25.3°C ± 0.4°C (2008) and 23.7°C ± 0.6°C (2009).

The turtle experienced a significant seasonal temperature difference on the nesting beach, with a corresponding difference in behavior for each season. Thus, evidence is that the turtle modifies its reliance upon temperature as a guide to locate a suitable nest site. In

2008 for example, the turtle experienced warmer temperatures, and may have relied on temperature more to locate a nest, because sediment temperatures were closer to her own.

In the 2009 season, the mean temperature of Casey Key was cooler, so temperature may have been a less reliable cue.

Only three events were sampled from this turtle in each season. It is difficult to determine Wiblet’s behavior and use of thermal cues based on two seasons of thermal data collection, out of the eight seasons she has been sited on Casey Key. Another thermal study focused on data collection from remigrants should be considered in the future.

Figure 28. Box plot of the mean temperature of all locations measured within crawl tracks of nest events made by Wiblet on Casey Key in 2008 and 2009.

Weather

In 2008 the mean temperature of the body pit (BP1), eggs (EGG), and gular skin of the turtle (GULAR) were significantly different for factors of wind, but not rain or cloud cover (BP1, EGG, GULAR combined; wind: Wilcoxon rank sum test; Z = -2.20; p

= 0.028; n = 9; rain: Wilcoxon rank sum test; Z = 0.648; p = 0.517; n = 9; clouds:

Wilcoxon rank sum test; Z = 1.43; p = 0.154; n = 9). All other mean temperatures within the crawl tracks of the nest events, including the water, waterline, wet sand, and dry sand, were not significantly different according to rain, wind or cloud cover. Adjacent to the tracks, there was a significant difference in the mean temperatures of wet sand (WS), dry sand (DS), and the sediment adjacent to the body pit (BP1), eggs (EGG), and gular skin

Figure 29. Box plot of the mean temperature of all locations measured one meter adjacent to the crawl tracks of nest events made by Wiblet on Casey Key in 2008 and 2009.

of the turtle (GULAR) according to rain (WS, DS combined: Wilcoxon rank sum test; Z

= -2.13; p = 0.033; n = 12; BP1, EGG, GULAR combined: Wilcoxon rank sum test; Z = -

2.20; p = 0.028; n = 9). However, these locations were insignificantly different according to wind and cloud cover. The mean temperatures of the remaining locations adjacent to the tracks, including the water and waterline, were not significantly different according to rain, wind, or cloud cover.

In 2009 the mean temperatures of all locations measured within the tracks of

Wiblet’s events, including the water, waterline, wet sand, dry sand, shell debris, the body

pit, nest chamber and gular skin of the turtle, were significantly different according to both wind and cloud cover (wind: Wilcoxon rank sum test; Z = -2.27; p = 0.023; n = 16; clouds: Wilcoxon rank sum test; Z = -2.27; p = 0.023; n = 16). The same is true for mean temperatures measured adjacent to the tracks (wind: Wilcoxon rank sum test; Z = 0.041; p = -2.04; n = 16; clouds: Wilcoxon rank sum test; Z = 0.041; p = -2.04; n = 16). No data were taken in the presence of rain; therefore, rain was not assessed this season.

The thermal data from Wiblet’s events demonstrate the potential for beach temperatures to be significantly augmented by factors of rain, wind or clouds.

Additionally, these results show that significant temperature differences are seen in events measured from a single turtle. However, the results should be treated with caution as statistical testing for weather conditions utilized a sample size of 12 or less. Also, these results cannot definitively prove that weather conditions were the single cause for the significant temperature differences measured from the beach locations. A controlled experiment that would allow for isolation of and separate testing of single weather events upon beach sediment would need to be performed to answer this problem, which is not possible. Therefore, these results cannot provide any conclusions about how weather may affect turtle nesting behavior and use of temperature while on the nesting beach.

Case Study 2: Serial Measurements of a Neophyte Loggerhead

Thermal Relationships

Pepper was an adult female loggerhead turtle that was recorded initially as a neophyte nesting turtle on Casey Key in 2008. Data were collected from Pepper’s four

nests and corresponding crawl tracks. Within the crawl tracks of these events, the mean temperature of her gular skin was thermally similar to the water (W), the dunes (DUNE), high tide line (HTL), and the body pit (BP1) (GULAR, W: Wilcoxon rank sum test ; Z =

1.59; p = 0.112; n = 8; GULAR, DUNE: Wilcoxon rank sum test; Z = -1.62; p = 0.105; n

= 6; GULAR, HTL: Wilcoxon rank sum test ; Z = -1.06; p = 0.289; n = 5; GULAR, BP1:

Wilcoxon rank sum test; Z = -1.01; p = 0.312; n = 8). These results for serial nests by an individual neophyte indicate that the nest temperature and the turtle’s temperature were thermally similar. However, these results should be treated with caution as the sample size for this turtle is low (n = 8 or less).

Serial datasets from both Pepper, a neophyte, and Wiblet, a remigrant, found a thermal similarity between their gular skin and the nesting beach. A speculation is that nest site selection uses common attributes by both experienced and inexperienced females. Independent mechanisms for nest site selection need not apply when turtles make nesting excursions. Turtles seem to have the ability to utilize environmental information, independent of their nesting experience.

Weather

Cloud cover was only assessed for Pepper’s nest events in 2008. The data from her nests did not include instances of rain, nor windy conditions. Therefore, temperature differences according to rain and wind could not be assessed. The mean temperatures of all locations assessed within, and adjacent to Pepper’s nest events, which included water

(W), waterline (WL), wet sand (WS), dry sand (DS), body pit (BP1), eggs (EGG) and gular skin of the turtle (GULAR), were not significantly different according to cloud

cover. Therefore, weather was not shown to be a factor in the nesting process of this turtle. However, there is low statistical power in this statement because the sample sizes were so low (W, WL, BP1, EGG, GULAR: n = 4; WS: n = 6; DS: n = 23).

Supplementary Thermal Data Retrieved from Additional Loggerhead Rookeries

In depth analyses of thermal data collected from several other loggerhead rookeries in the United States and Australia are provided in the appendices (Appendices

2-8). The data suggest that there are significant thermal differences between different nesting beaches within the same season (Appendix 4) and that there is potential for female loggerheads to use thermal cues while selecting a nest site (Appendix 2;

Appendices 5-8).

The use of sand surface temperatures by gravid females on these other rookeries can be summarized by three main conclusions. First, thermal cues may be integrated into the decision to commit to a false crawl event or a nest event, as the mean temperature of these two events was significantly different on several rookeries, including Casey Key in the 2007 nesting season (Appendix 2), Little Cumberland Island in 1982 (Appendix 5), and Wassaw Island in 2008 and 2009 (Appendix 7). Secondly, the gular skin of nesting females was thermally similar to the body pit on nearly all rookeries measured, with the single exception of Little Cumberland Island (Appendix 5). This finding may indicate that turtles use temperature to locate a nest site. More specifically, they may search for a location thermally similar to their gular skin. Thirdly, the majority of sediment locations that lead up to the apex of a false crawl or a nest were all thermally similar. Therefore,

turtles likely do not discriminate among locations to guide them to a nest location, because significantly thermal differences are not present at these rookeries.

CHAPTER 5 – BROADER IMPLICATIONS AND CONCLUSIONS

Broader Implications

The loggerhead sea turtle is listed as Endangered on the IUCN Red List and

Threatened under the U.S. Endangered Species Act (Witherington et al., 2009). In order to effectively manage this species, we need to understand what cues are involved in nest site choice, to what degree they are used, and any patterns in usage that develop over time. This way, we may understand when and how to most effectively protect nesting beaches and ensure that this species continues to endure the test of time.

Another looming threat to marine turtles, beyond their population size, is that of global climate change. Air temperatures have increased to levels that have not been seen since records began in 1850, and global mean ocean temperatures are thought to be 0.7°C warmer than at any time in the last 420,000 years, with an expectation that these warming trends will increase at accelerated rates (Hoegh-Guldberg et al., 2007; Hawkes et al.,

2009). Sea turtles may be uniquely sensitive to such an accelerated warming trend because of their slow growth to sexual maturity, temperature-dependent sex determination (TSD), and natal beach homing (Mrosovsky et al., 1984; Davenport, 1989;

Davenport, 1997). Even temperature increases of a few tenths of a degree Celsius may skew reproduction in favor of female production (Davenport, 1997).

In addition, with increased air and water temperatures, the world’s ocean will thermally expand to accommodate the influx of heat, which may result in a sea level rise of 18 to 60 cm by 2100 (Meehl et al., 2005; IPCC, 2007). This increase in sea level may change or compromise the availability of some nesting beaches, like low-lying, narrow, coastal and island beaches, like the barrier island nesting beach of Casey Key (Fish et al.,

2005; Baker et al., 2006; Jones et al., 2007; Hawes et al., 2009; Mazaris et al., 2009).

This may impede or seriously deter sea turtles from nesting on natal beaches. On the other hand, climate change may also increase the proportion of thermally suitable nesting habitat, geographically and temporally (Hawkes et al., 2009). Increased air temperatures may thermally alter nesting beaches, making previously suitable nesting beaches unsuitable or alternatively, making previously unsuitable beaches, like those of more northerly latitudes, suitable for successful nesting incubation (Hawes et al., 2009). Such thermal alterations to terrestrial and marine environments may significantly modify the use of thermal cues by gravid females during nest site selection as well.

Increased air temperatures may also increase the length of time the nesting season lasts and may even facilitate year-round nesting (Pike et al., 2006; Yasuda et al., 2006).

However, data are lacking on how quickly sea turtles would be able to adapt to these changes (Hawkes et al., 2009). Therefore, turtles exposed to this increase in temperatures may not be able to adapt to relatively drastic changes in the thermal environment, especially because climate change in the past appears to have been much more gradual

(Davenport, 1997). Furthermore, overexploitation and habitat loss has yielded decreased populations of sea turtles in recent years; combine this with climate change, and the species resiliency may be compromised in the future.

Another threat to nesting beaches is human influence in the form of beach renourishment. Massive dredge-and-fill projects have become a common method of combating shoreline retreat (Peterson and Bishop, 2005). Material transplanted onto the nesting beach may significantly alter nesting beach conditions and may produce improper incubation conditions. Even if effort is taken to use beach quality sand, transplanted sand may be a different grain size, moisture content, sheer resistance and temperature than that of native sand (Herren, 1999). Introduction of non-native sand can alter reproductive success by altering the nest sand environment and can also prevent females from crawling to a preferred nesting site by introducing a physical barrier, such as a scarp or step cliff (Steinitz et al., 1998; Herren, 1999). Barriers such as exposed seawalls have been shown to change the spatial distribution of nests on the nesting beach, in that nests are made seaward of the barrier zone, which increases the risk of egg mortality from erosion and inundation (Witherington et al., 2011). If beach nourishment provides such a physical barrier to nesting, it is certainly possible that egg mortality could increase, especially the year in which renourishment occurs.

Renourished beaches tend to have greater thermal conductivity as a consequence of higher water content than natural beaches (Ackerman, 1997). Increased water content increases the heat capacity of the beach, resulting in significantly different thermal properties of renourished and natural beaches on a daily and seasonal basis (Ackerman,

1997). Temperature data from hatchery nests incubated in native silicate sand from

Fisher Island, Dade County, Florida and imported oolitic aragonite sand from Ocean Cay

Bahamas in the 1991-1993 nesting season suggested that incubation temperatures are significantly different in each type of sand (Milton et al., 1997). The imported aragonite

sand was consistently significantly cooler than the native silicate sand; so much so that it had the potential to alter sex ratios such that the imported sand could have potentially produced predominately if not exclusively male hatchlings (Milton et al., 1997).

Hatching and nesting success can also be affected. Hatching success on

Melbourne Beach, Florida was significantly reduced in the 1996 and 1997 nesting seasons on nourished beaches because higher moisture content in the nourishment sand may have impeded gas exchange (Herren, 1999). Another study performed on one nourished beach and two natural beaches in Palm Beach County, Florida found that nesting declined by 4.4 to 5.4 nests per kilometer per day and false crawls increased by

5.0 to 5.6 false crawls per kilometer per day the first nesting season following beach renourishment (Rumbold et al., 2001). However, in the second season following renourishment nesting was only reduced by 0.5 to 1.6 per kilometer per day and false crawls frequency was 0.7 to 0.9 false crawls per kilometer per day (Rumbold et al.,

2001). Therefore, impacts to nesting were most severe the first season after renourishment, with significant recovery in the second season. Many loggerheads nesting on Jupiter Island, Florida abandoned nesting attempts just after a renourishment project, potentially attributable to increased surface hardness of the nesting beach and berm formation (Steinitz et al., 1998). After two years, berms were rarely present, surface hardness decreased, and nest densities were comparable to densities on natural beaches (Steinitz et al., 1998). However, subsequent nesting seasons on Jupiter Island saw nest densities declining due to erosion of the renourished beach (Steinitz et al.,

1998). While impacts from beach renourishment can be serious, the turtles do seem to

have the ability to adapt to the new sediment characteristics. Perhaps their adaptability to new sediment conditions can extend to changes in global temperatures as well.

Overall, considering the 970 nourishment projects that have taken place throughout the country since its inception in 1922, there is a relatively high uncertainty involved in predicting biological impacts of beach nourishment projects (Peterson and

Bishop, 2005). The possibility of thermal disruption is evident and it has the potential to significantly affect successful nesting of sea turtles, and thus the future of the species.

Perhaps a species specific monitoring program should be introduced as a requirement for nourishment federally and state granted permits in the future, especially considering that the biological risk is far greater than the ephemeral reward.

Conclusions

One beach characteristic that has not been investigated extensively is sediment temperature. Stoneburner and Richardson began investigating the effects of temperature in 1981; the results of the study and temperature theory were all but dismissed as investigative error, or in lieu of some other environmental factor such as vegetation, or pure random selection (Hays and Speakman, 1993; Hays et al., 1995; Kamel and

Mrosovsky, 2005, 2006). Wood and Bjorndal (2000) seems to be one of very few studies that has recently investigated temperature as part of their study, but they too dismissed temperature as an unimportant factor in nest site selection, suggesting that the slope of the beach is the most important to a loggerhead turtle during the selection process. When temperature was revisited by López-Castro et al. (2004), temperature was indeed found to

be important to nest site selection for olive ridley turtles- they preferred to nest in locations near 32°C.

The aim of the current study was to reinvestigate how thermal properties of the nesting beach may be influencing nest site selection by loggerhead sea turtles. My study found that an IR thermometer is appropriate to use to measure both sediment temperatures and surface temperatures of the turtles in the field, and this is the first study to show the efficacy of this device in sea turtle field work. In addition, based on thermal data from several loggerhead rookeries, my study suggests that loggerhead turtles can potentially use the thermal cues across a beach transect to locate a suitable nest site by seeking a match of sand temperature against the gular skin temperature of the gravid female.

Females may utilize the temperature of their gular skin to select the most reliable nest site because their gular skin temperature is an effective proxy for water temperature.

Loggerheads spend the majority of their lives in a marine environment and maintain a small (1-2°C) temperature difference between the body core and the water (Spotila et al.,

1997). Therefore, body temperature may become a reliable source of information they can draw from to select a satisfactory nest site while operating in an unfamiliar terrestrial environment.

However, temperature may not be used consistently within seasons or between seasons on every nesting beach. Instead, it may be integrated into the nest site decision that is influenced by other physical cues, such as slope of the nesting beach. Due to the variable importance of temperature over seasons and nesting beaches, most likely due to the independent analysis of beach characteristics during each terrestrial excursion,

temperature appears to have limited predictive power for nest site selection of loggerhead turtles in future nesting seasons. This has been seen in other studies where individual leatherbacks showed individual nesting patterns, with much within-individual variation which yielded a lack of predictability in nesting patterns (Kamel and Mrosovsky, 2004).

While it is possible that turtles use multiple cues to choose the most suitable nest location, there must be an evolutionary advantage to doing so; otherwise the behavior would not be present in the species. Sea turtles (Cheloniidae, Dermochelyidae) were all established by the Cretaceous period (Pritchard, 1997). Because sea turtles have survived since at least the end of the Cretaceous period, 65.5 million years ago, evolution demands that they adapt to an environment that has been changing over millions of years. In order to adapt, turtles must be able to use multiple sources of information, be it from the environment, from themselves, or other sources and integrate them to make the best choice of nest site. By using this integrative process independently upon each emersion onto the nesting beach, they ensure that at least some of their offspring survive. Nest site selection by the leatherback sea turtle has been described as highly variable and widely dispersed (Weishampel et al., 2003; Caut et al., 2006). It is certainly possible that this is in response to an integrative decision process, developed over millions of years, or a function of bet-hedging to ensure the survival of at least some offspring. However, it is hard to say if two years of nesting data on Casey Key can begin to explain a behavior that has had time to develop for millions of years.

Temperature is of profound importance as an environmental factor for marine turtles, affecting features of their life history from the embryonic stage (incubation period and hatchling sex determination) to the adult stage (distribution, behavior, physiology

and ecology) (Yntema and Mrosovsky, 1980; Spotila and Standora, 1985; Seebacher and

Franklin, 2005; Hawkes et al., 2009). If temperature has such an important influence on the life history of turtles, it is reasonable to suggest that temperature may play some role, be it variable over each season or each individual nesting event, in nest site selection. It is the hope of this study that temperature continues to be considered in future studies among a host of other cues to determine the variability in cue use and potential patterns that emerge.

LIST OF REFERENCES

Ackerman, R.A. 1997. The nest environment and the embryonic development of sea turtles. Pp. 83-106 in P.L. Lutz and J.A. Musick (Eds.), The Biology of Sea Turtles. CRC Press, USA.

Baker, J.D., C.L. Littnan, and D.W. Johnston. 2006. Potential effects of sea level rise on the terrestrial habitats of endangered and endemic megafauna in the Northwestern Hawaiian Islands. Endangered Species Research 2: 21-30.

Blamires, S.J., M.L. Guinea, and R.I.T. Prince. 2003. Influence of nest site selection on predation of flatback sea turtle (Natador depressus) eggs by varanid lizards in Northern Australia. Chelonian Conservation and Biology 4: 557-563.

Bolten, A.B., and B.E. Witherington (Eds.). 2003. Loggerhead Sea Turtles. Smithsonian Books, USA.

Bowen, K.D., R.-J. Spencer, and F.J. Janzen. 2005. A comparative study of environmental factors that affect nesting in Australian and North American freshwater turtles. Journal of Zoology 267: 397-404.

Burke, V.J., J.W. Gibbons, and J.L. Greene. 1994. Prolonged nesting forays by common mud turtles (Kinosternon subrubrum). American Midland Naturalist 131: 190- 195.

Byrkit, D.R. 1980. Elements of Statistics: An Introduction to Probability and Statistical Inference, Third Edition. D. Van Nostrand Company, USA.

Caldwell, D.K. 1962. Comments on the nesting behavior of Atlantic loggerhead sea turtles, based primarily on tagging returns. Quarterly Journal Florida Academy of Sciences 25: 287-302.

Camhi, M.D. 1993. The role of nest site selection in loggerhead sea turtle (Caretta caretta) nest success and sex ratio control. Ph.D. Dissertation, Rutgers University, New Brunswick, New Jersey.

Caut, S., E. Guirlet, P. Jouquet, and M. Girondot. 2006. Influence of nest location and yolkless eggs on the hatching success of leatherback turtle clutches in French Guiana. Canadian Journal of Zoology 84: 908-915.

Chen, H-C., I.-Jiunn Cheng, and E. Hong. 2007. The influence of the beach environment on the digging success and nest site distribution of the green turtle, Chelonia mydas, on Wan-an Island, Penghu Archipelago, Taiwan. Journal of Coastal Research 23: 1277-1286.

Conant, T.A., P.H. Dutton, T. Eguchi, S.P. Epperly, C.C. Fahy, M.H. Godfrey, S.L. MacPherson, E.E. Possardt, B.A. Schroeder, J.A. Seminoff, M.L. Snover, C.M. Upite, and B.E. Witherington. 2009. Loggerhead sea turtle (Caretta caretta) 2009 status review under the U.S. Endangered Species Act. Report of the Loggerhead Biological Review Team to the National Marine Fisheries Service, August 2009. 222 pages.

Davenport, J. 1989. Sea turtles and the greenhouse effect. British Herpetological Society Bulletin 29: 11-15.

Davenport, J. 1997. Temperature and the life-history strategies of sea turtles. Journal of Thermal Biology 22:479-488.

Dodd, C.K. 1988. Synopsis of the biological data on the loggerhead sea turtle Caretta caretta (Linnaeus 1758). USFWS Biological Report 88 (14).

Ficetola, G.F. 2007. The influence of beach features on nesting of the hawsbill turtle Eretmochelys imbricata in the Arabian Gulf. Oryx 41: 402-405.

Fish, M.R., I.M. Cote, J.A. Gill, A.P. Jones, S. Renshoff, and A.R. Watkinson. 2005. Predicting the impact of sea-level rise on Caribbean sea turtle nesting habitat. Conservation Biology 19: 482-491.

Foley, A.M., S.A. Peck, G.R. Harman, and L.W. Richardson. 2000. Loggerhead turtle (Caretta caretta) nesting habitat on low-relief mangrove islands in southwest Florida and consequences to hatchling sex ratios. Herpetologica 56: 433-445.

Frazer, N.B., and L.M. Ehrhart. 1985. Preliminary growth models for green, Chelonia mydas, and loggerhead, Caretta caretta, turtles in the wild. Copeia 1985: 73-79.

Frazer, N.B., C.J. Limpus, and J.L. Greene. 1994. Growth and estimated age at maturity of Queensland loggerheads. Pp. 42-46 in: K.A. Bjorndal et al. (compilers). Proceedings of the Fourteenth Annual Symposium on Sea Turtle Biology and Conservation. NOAA Technical Memorandum. NMFS-SEFSC-351.

Garcon, J.S., A. Grech, J. Moloney, and M. Hamann. 2010. Relative Exposure Index: an important factor in sea turtle nesting distribution. Aquatic Conservation-Marine and Freshwater Ecosystems 20: 140-149.

Garmestani, A.S., H.F. Percival, K.M. Portier, and K.G. Rice. 2000. Nest-site selection by the loggerhead sea turtle in Florida’s Ten Thousand Islands. Journal of Herpetology 34: 504-510.

Hare, J.R., E. Whitworth, and A. Cree. 2007. Correct orientation of a hand-held infrared thermometer is important for accurate measurement of body temperatures in small lizards and Tuatara. Herpetological Review 38: 311-315.

Hawkes, L.A., A.C. Broderick, M.H. Godfrey, and B.J. Godley. 2009. Climate change and marine turtles. Endangered Species Research 7: 137-154.

Hays, G.C., and J.R. Speakman. 1993. Nest placement by loggerhead turtles, Caretta caretta. Animal Behaviour 45: 47-53.

Hays, G.C., A. Mackay, C.R. Adams, J.A. Mortimer, J.R. Speakman, and M. Boerema. 1995. Nest site selection by sea turtles. Journal of the Marine Biological Association of the United Kingdom 75: 667-674.

Herren, R.M. 1999. The effect of beach nourishment on loggerhead (Caretta caretta) nesting and reproductive success at Sebastian Inlet, Florida. M.S. Thesis, University of Central Florida, Orlando, Florida.

Hoegh-Guldberg, O., P.J. Mumby, A.J. Hooten, R.S. Steneck, P. Greenfield, E. Gomez, C.D. Harvell, P.F. Sale, A.J. Edwards, K. Caldeira, N. Knowlton, C.M. Eakin, R. Iglesias-Prieto, N. Muthiga, R.H. Bradbury, A. Dubi, and M.E. Hatziolos. 2007. Coral reefs under rapid climate change and ocean acidification. Science 318: 1737-1742.

Horrocks, J.A., and N.M. Scott. 1991. Nest site location and nest success in the hawksbill turtle (Eretmochelys imbricata) in Barbados, West Indies. Marine Ecology Progress Series 69: 1-8.

Hughes, G.R., and A. Mentis. 1967. Further studies on marine turtles in Tongaland, 2. Lammergeyer 3: 55-72.

IPCC (Intergovernmental Panel on Climate Change). 2007. Summary for Policymakers. Cambridge University Press, United Kingdom.

Johannes, R.E., and D.W. Rimmer. 1984. Some distinguishing characteristics of nesting beaches of the green turtle Chelonia mydas on North West Cape Peninsula, Western Australia. Marine Biology 83: 149-154.

Jones, A.R., W. Gladstone, and N.J. Hacking. 2007. Australian sandy beach ecosystems and climate change: ecology and management. Australian Zoologist 34: 190-202.

Kamel, S.J., and N. Mrosovsky. 2004. Nest site selection in leatherbacks, Demochelys coriacea: individual patterns and their consequences. Animal Behaviour 68: 357- 366.

Kamel, S.J., and N. Mrosovsky. 2005. Repeatability of nesting preferences in the hawksbill sea turtle, Eretmochelys imbricata, and their fitness consequences. Animal Behaviour 70: 819-828.

Kamel, S.J., and N. Mrosovsky. 2006. Inter-seasonal maintenance of individual nest site preferences in hawksbill sea turtles. Ecology 87: 2947-2952.

Kaska, Y., E. Baskale, R. Urhan, Y. Katilmis, M. Gidis, F. Sari, D. Sozbilen, A.F. Canbolat, F. Yilmaz, M. Barlas, N. Ozdemir, and M. Ozkul. 2010. Natural and anthropogenic factors affecting the nest-site selection of loggerhead turtles, Caretta caretta, on Dalaman-Sarigerme beach in south-west Turkey. Zoology in the Middle East 50: 47-58.

Kikukawa, A., N. Namezaki, K. Hirate, and H. Ota. 1998. Factors affecting nesting beach selection by sea turtles: A multivariate approach. Pp. 65-66 in: S.P. Eperly, and J. Braun (compilers). Proceedings of the 17th annual symposium on sea turtle biology and conservation. NOAA Technical Memorandum. NMFS-SEFSC-415.

Kikukawa, A., N. Namezaki, K. Hirate, and H. Ota. 1999. Factors affecting nesting beach selection by loggerhead turtles (Caretta caretta): A multivariate approach. Journal of Zoology 249: 447-454.

Lenarz, M.S., N.B. Frazer, M.S. Ralston, and R.B. Mast. 1981. Seven nests recorded for loggerhead turtle (Caretta caretta) in one season. Herpetological Review 12: 9.

Limpus, C.J. 1985. A study of the loggerhead sea turtle, Caretta caretta, in eastern Australia. Ph.D. Dissertation, University of Queensland, St. Lucia, Australia.

López-Castro, M.C., R. Carmona, and W.J. Nichols. 2004. Nesting characteristics of the olive ridley turtle (Lepidochelys olivacea) in Cabo Pulmo, southern Baja California. Marine Biology 145: 811-820.

Lund, F. 1986. Nest production and nesting site tenacity of the loggerhead turtle, Caretta caretta, on Jupiter Island, Florida. M.S. Thesis, University of Florida, Gainsville, Florida.

Lutz, P.L., and J.A. Musick (Eds.). 1997. The Biology of Sea Turtles. CRC Press, USA.

Lutz, P.L., J.A. Musick, and J. Wyneken (Eds.). 2003. The Biology of Sea Turtles Volume II. CRC Press, USA.

Martin, R.E., R.G. Ernest, N. Williams-Walls, J.R. Wilcox. 1989. Long-term trends in sea turtle nesting on Hutchinson Island, Florida. Pp. 111-113 in: S.A. Eckert, K.L. Eckert, and T.H. Richardson (compilers). Proceedings of the ninth annual workshop on sea turtle biology and conservation. NOAA Technical Memorandum. NMFS-SEFSC-232.

Mazaris, A.D., Y.G. Matsinos, D. Margaritoulis. 2006. Nest site selection of loggerhead sea turtles: The case of the island of Zakynthos, W Greece. Journal of Experimental Marine Biology and Ecology 336: 157-162.

Mazaris, A.D., G. Mastinos, and J.D. Pantis. 2009. Evaluating the impacts of coastal squeeze on sea turtle nesting. Ocean & Coastal Management 52: 139-145.

Meehl, G.A., W.M. Washington, W.D. Collins, J.M. Arblaster, H. Aixue, L.E. Buja, W.G. Strand, and H. Teng. 2005. How much more global warming and sea level rise? Science 307: 1769-1772.

Mellanby, R.J., A.C. Broderick, and B.J. Godley. 1998. Nest site selection in Mediterranean marine turtles at Chelones Bay, Northern Cyprus. Pp. 103-104 in: R. Byles, and Y. Fernandez (compilers). Proceedings of the 16th annual symposium on sea turtles biology and conservation. NOAA Technical Memorandum. NMFS-SEFSC-412.

Mendonca, M.T. 1981. Comparative growth rates of wild immature Chelonia mydas and Caretta caretta in Florida. Journal of Herpetology 15: 444-447.

Miller, J.D., C.J. Limpus, and M.H. Godfrey. 2003. Nest site selection, oviposition, eggs, development, hatching, and emergence of loggerhead turtles. Pp. 125-143 in A.B. Bolten, and B.E. Witherington (Eds.), Loggerhead Sea Turtles. Smithsonian Books, USA.

Milton, S.L., A.A. Schulman, and P.L. Lutz. 1997. The effect of beach nourishment with aragonite versus silicate sand on beach temperature and loggerhead sea turtle nesting success. Journal of Coastal Research 13: 904-915.

Mrosovsky, N. 1983. Ecology and nest-site selection of leatherback turtles Dermochelys coriacea. Biological Conservation 26: 47-56.

Mrosovsky, N., S.R. Hopkins-Murphy, and J.I. Richardson. 1984. Sex ratio of sea turtles: seasonal changes. Science 225: 739-741.

NMFS (National Marine Fisheries Service). 2001. Stock assessments of loggerhead and leatherback sea turtles and an assessment of the impact of the pelagic longline fishery on the loggerhead and leatherback sea turtles of the western north Atlantic. U.S. Department of Commerce, NOAA Technical Memorandum.

NMFS-SEFSC-455. Document available online: http://www.sefsc.noaa.gov/turtles/TM_455_NMFS.pdf.

Peterson, C.H., and M.J. Bishop. 2005. Assessing the environmental impacts of beach nourishment. Bioscience 55: 887-896.

Pike, D.A. 2008. Environmental correlates of nesting in loggerhead turtles, Caretta caretta. Animal Behaviour 76: 603-610.

Pike, D.A., R.L. Antworth, and J.C. Stiner. 2006. Earlier nesting contributes to shorter nesting seasons for the loggerhead sea turtle, Caretta caretta. Journal of Herpetology 40: 91-94.

Pritchard, P.C.H. 1997. Evolution, phylogeny, and current status. Pp. 1-28 in P.L. Lutz and J.A. Musick (Eds.), The Biology of Sea Turtles. CRC Press, USA.

Rowley, J.J.L., and R.A. Alford. 2007. Non-contact infrared thermometers can accurately measure amphibian body temperatures. Herpetological Review 38: 308-311.

Rumbold, D.G., P.W. Davis, and C. Perretta. 2001. Estimating the effect of beach nourishment on Caretta caretta (loggerhead sea turtle) nesting. Restoration Ecology 9: 304-310.

Sall, J., A. Leman, and L. Creighton. 2001. JMP start statistics: a guide to statistics and data analysis. SAS Institute, Pacific Grove, CA, USA.

Sea Turtle Conservation and Research Program, Mote Marine Laboratory. Unpublished raw data.

Seebacher, F., and C.E. Franklin. 2005. Physiological mechanisms of thermoregulation in reptiles: a review. Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 175: 533-541.

Serafini, T.Z., G.G. Lopez, and P.L. Bernardo de Rocha. 2009. Nest site selection and hatching success of hawksbill and loggerhead sea turtles (Testudines, Cheloniidae) at Arembepe Beach, northeastern Brazil. Phyllomedusa 8: 3-17.

Spanier, M.J. 2010. Beach erosion and nest site selection by the leatherback sea turtle Dermochelys coriacea (Testudines: Dermochelyidae) and implications for management practices at Playa Gandoca, Costa Rica. Revista de Biología Tropical 58: 1237-1246.

Spotila, J.R., and E.A. Standora. 1985. Environmental constraints on the thermal energetics of sea turtles. Copeia 1985: 694-702.

Spotila, J.R., M.P. O’Connor, and F.V. Paladino. 1997. Thermal biology. Pp. 297-314 in P.L Lutz, and J.A. Musick (Eds.), The Biology of Sea Turtles. CRC Press, USA.

Steinitz, M.J., M. Salmon, and J. Wyneken. 1998. Beach renourishment and loggerhead turtle reproduction: A seven year study at Jupiter Island, Florida. Journal of Coastal Research 14: 1000-1013.

Stoneburner, D.L., and J.I. Richardson. 1981. Observations on the role of temperature in loggerhead turtle nest site selection. Copeia 1: 238-241.

Talbert, O.R., Jr., S.E. Stancyk, J.M. Dean, and J.M. Will. 1980. Nesting activity of the loggerhead turtle (Caretta caretta) in South Carolina. 1. A rookery in transition. Copeia 1980: 709-718.

Tucker, A.D. 2009. Eight nests recorded for a loggerhead turtle within one season. Marine Turtle Newsletter 124: 16-17.

Tucker, A.D. 2010. Nest site fidelity and clutch frequency of loggerhead turtles are better elucidated by satellite telemetry than by nocturnal tagging efforts: Implications for stock estimation. Journal of Experimental Marine Biology and Ecology 383: 48-55.

Turkozan, O., K. Yamamoto, and C. Yilmaz. 2011. Nest site preference and hatching success of green (Chelonia mydas) and loggerehead (Caretta caretta) sea turtles at Akyatan Beach, Turkey. Chelonian Conservation and Biology 10: 270-275.

Weishampel, J.F., D.A. Bagley, L.M. Ehrhart, and B.L. Rodenbeck. 2003. Spatiotemporal patterns of annual sea turtle nesting behaviors along an East Central Florida beach. Biological Conservation 110: 295-303.

Wentworth, C.K. 1922. A scale of grade and class terms for clastic sediments. Journal of Geology 30: 377-392.

Whitmore, C.P., and P.H. Dutton. 1985. Infertility, embryonic mortality and nest-site selection in leatherback and green sea turtles in Suriname. Biological Conservation 34: 251-272.

Wilson, D.S., H.R. Mushinsky, and E.D. McCoy. 1999. Nesting behavior of the striped mud turtle, Kinosternon baurii (Testudines: Kinosternidae). Copeia 1999: 958- 968.

Witherington, B.E. 1992. Behavioral response of nesting turtles to artificial lighting. Herpetologica 48: 31-39.

Witherington, B. E., and R. E. Martin. 1996. Understanding, assessing, and resolving light-pollution problems on sea turtle nesting beaches. Florida Marine Research Institute Technical Report TR-2. 73 p.

Witherington, B., P. Kubilis, B. Brost, and A. Meylan. 2009. Decreasing annual nest counts in a globally important loggerhead sea turtle population. Ecological Applications 19: 30-54.

Witherington, B., S. Hirama, and A. Mosier. 2011. Sea turtle responses to barriers on their nesting beach. Journal of Experimental Marine Biology and Ecology 401: 1- 6.

Wood, D.W., and K.A. Bjorndal. 2000. Relation of temperature, moisture, salinity, and slope to nest site selection in loggerhead sea turtles. Copeia 2000: 119-128.

Yalҫin-Özdilek, Ş., H.S. Özdilek, and F.S. Ozaner. 2007. Possible Influence of beach sand characteristics on green turtle nesting activity on Samandağ Beach, Turkey. Journal of Coastal Research 23: 1379-1390.

Yasuda, T., H. Tanaka, K. Kittiwattanawong, H. Mitamura, W. Klom-In, and N. Arai. 2006. Do female green turtles (Chelonia mydas) exhibit reproductive seasonality in a year round nesting rookery? Journal of Zoology 269: 451-457.

Yntema, C.L., and N. Mrosovsky. 1980. Sexual differentiation in hatchling loggerheads (Caretta caretta) incubated at different controlled temperatures. Herpetologica 36: 33-36.

APPENDIX 1 – ADDITIONAL FIGURES

Figure A1. Box plot of the mean temperatures of all locations measured within the crawl tracks of all false crawl events measured on Casey Key in 2008.

Figure A2. Box plot of the mean temperatures of all locations measured within the crawl tracks of all nest events measured on Casey Key in 2008.

Figure A3. Box plot of the mean temperatures of all locations measured one meter adjacent to the crawl tracks of both false crawl and nest events on Casey Key in 2008.

Figure A4. Box plot of the mean temperatures of all locations measured within the crawl tracks of both false crawl and nest events on Casey Key in 2009.

Figure A5. Box plot of the mean temperatures of all locations measured one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2009.

Figure A6. Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events completed by Wiblet on Casey Key in 2008.

APPENDIX 2 – CASEY KEY 2007

Thermal Relationships

Temperature data were available from Casey Key in 2007, where the IR thermometer was used for data collection of 24 false crawl events and 28 nest events.

There was a significant thermal difference between false crawl and nest events both within the crawl tracks and one meter adjacent to the crawl tracks of these events (within crawl: t-test; t = -3.74; p = 0.0002; n = 404; one meter adjacent: t-test; t = -4.72; p <

0.0001; n = 392). Within the crawl, the mean temperature of false crawl events was

25.0°C ± 0.2°C and that of nest events was 23.9°C ± 0.2°C. Mean sediment temperatures one meter adjacent to false crawl events was 25.1°C ± 0.2°C, while that adjacent to nest events was 23.7°C ± 0.2°C.

There was a significant thermal difference in mean temperatures among all locations measured within the crawl tracks of nest events (Fig. A7; One-way ANOVA; F

= 8.52; p < 0.0001; n = 288). A Tukey-Kramer post hoc test revealed that the nest chamber (NC1), mean high water mark (MHW) and dunes (DUNE) were thermally similar to all locations measured within the crawl tracks of nest events (Table A1). Like the 2008 and 2009 seasons, the gular skin of nesting turtles was thermally similar to the body pit (Table A1; Tukey-Kramer post hoc test; p = 0.355). The gular skin of the turtles

100

Figure A7. Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events on Casey Key in 2007.

was also thermally similar to the water, waterline, and the body pit attempt made closest to the water (BP3) (Tukey-Kramer post hoc test). The gular skin of the turtles was significantly different from the body pit attempt made prior to nest construction (BP2)

(Tukey-Kramer post hoc test; p = 0.024). Most sediment locations leading up to the nest site were thermally similar, including the waterline, wet sand, dry sand, high tide line, and berm (Table A1; Tukey-Kramer post hoc test). The body pit (BP1), and two body pit attempts (BP2, BP3) were thermally similar to one another, and also thermally similar to the waterline, wet sand, dry sand, high tide line and berm (Table A1; Tukey-Kramer post

101

Table A1. Mean temperatures of all locations measured within and one meter adjacent to the crawl tracks of false crawl and nest events on Casey Key in 2007. Subscripts indicate locations that were thermally similar (share the same letter) and significantly thermally different (do not share the same letter), for each column.

Temperature (°C) (standard error, °C) False Crawl Events Nest Events False Crawl Events Nest Events Location* Within the crawl Within the crawl One meter adjacent to the tracks One meter adjacent to the tracks

BERM ** 19.7 ± 1.5 C ** 19.9 ± 1.6 B

BP1 24.1 ± 0.9 B 24.1 ± 0.5 B, C 24.0 ± 1.0 B 23.9 ± 0.6 A, B

BP2 25.4 ± 1.2 A, B 20.1 ± 1.5 C 25.0 ± 1.4 A, B 19.6 ± 2.0 A, B

BP3 ** 19.8 ± 1.9 B, C ** 19.4 ± 2.0 A, B

DS 24.7 ± 0.3 B 23.4 ± 0.3 C 24.8 ± 0.3 B 23.3 ± 0.3 B

DUNE 25.3 ± 0.8 A, B 26.9 ± 1.5 A, B, C 25.6 ± 0.8 A, B 27.0 ± 1.6 A, B

102 EGG ** 27.2 ± 0.5 A ** 24.6 ± 0.6 A, B

GULAR ** 26.1 ± 0.6 A, B ** 25.4 ± 0.7 A, B

HTL ** 21.3 ± 1.0 C ** 21.0 ± 1.2 B

MHW 24.8 ± 0.5 B 24.7 ± 0.7 A, B, C 25.0 ± 0.6 B 24.5 ± 0.8 A, B

NC1 25.6 ± 1.9 A, B 26.6 ± 2.7 A, B, C 24.9 ± 2.0 A, B **

VEG 25.1 ± 1.9 A, B ** 24.2 ± 2.0 A, B **

W 27.8 ± 0.4 A 26.2 ± 0.5 A, B 27.7 ± 0.5 A 26.0 ± 0.5 A

WL 24.4 ± 0.4 B 23.9 ± 0.5 B, C 24.6 ± 0.5 B 23.7 ± 0.5 A, B

WS 24.0 ± 0.4 B 23.0 ± 0.5 C 24.2 ± 0.4 B 22.9 ± 0.5 B *See Table 6 for a description of most locations; MHW: mean high water; VEG: vegetation on the dunes (back beach). **These locations were not measured in the 2007 season on Casey Key.

hoc test).

Adjacent to nest events, the thermal relationships among locations was different than those within the crawls. All sediment locations were thermally similar, including the waterline, wet sand, dry sand, mean high water mark, high tide line, the berm, the dunes and the sediment adjacent to the body pit (BP1), two body pit attempts (BP2, BP3), the eggs, and gular skin of the turtles (Table A1; Tukey-Kramer post hoc test). This result suggests that differences in mean temperatures on the crawl were not due to the natural thermal variation in beach sediment along the beach. The relationships observed in locations on the tracks of nest events are therefore more likely due to the behavior of the turtles. In other words, turtles seemed to be actively searching thermal cues on the beach during a nesting event.

These results reinforce the possibility that turtles may search for a temperature thermally similar to their own gular skin when choosing a nest site, and agrees with the results of the 2008 and 2009 seasons. In addition, the gular skin of the turtles was also thermally similar to the body pit attempt made closest to the water (BP3), which also agrees with the results from the 2008 and 2009 seasons. Yet, turtles did not nest at BP3.

This result suggests that another environmental factor may be important in nest site choice. If temperature were the only important cue when considering a nest site, turtles would nest at the first beach location they encountered that was thermally similar to their gular skin, which would have been the waterline in the 2007 season. In the present study, no turtle was ever seen nesting at the waterline, therefore turtles must consider other environmental cues in addition to temperature. Turtles were also willing to attempt to nest in a location thermally dissimilar to their gular skin (BP2), just as in the 2008 season,

103

suggesting that other factors are involved in nest site selection and those factors may supersede the importance of temperature.

In addition, all the sediment locations within the tracks of false crawl events were all similar, including the waterline, wet sand, dry sand, mean high water, dunes, vegetation behind the dunes, two body pit attempts (BP1, BP2), and a nest chamber attempt (NC1) (Table A1; Tukey-Kramer post hoc test). The same thermal relationships were maintained one meter adjacent to the false crawl tracks (Table A1; Tukey-Kramer post hoc test). These results show that the turtles most likely were not able to thermally discriminate among beach locations during false crawl events. Alternatively, turtles may not use temperature when they false crawl. Perhaps turtles only utilize temperature after they have determined that they will nest during a particular excursion. If this is true, then other environmental parameters may be used by turtles in the decision to commit to a false crawl and nest event.

In 2007 there were significant differences in mean temperatures of false crawl events and nesting events within the crawl tracks. This association may imply that temperature was used by females to decide whether or not to nest. However, there were also significant differences in the mean temperature of false crawl events and nesting events one meter adjacent to the crawl tracks. These results imply that the sediment turtles encountered while false crawling was thermally different from the sediment turtles encountered during a nesting event. These findings suggest there is a potential for turtles to use temperature in a different way during a false crawl events than during a nest event.

Thus, these findings support the speculation of the present study that turtles may have used thermal cues in 2007 only when nesting, not when they false crawled.

104

In contrast, comparisons of mean temperatures of false crawl events and nest events within the crawl tracks in 2008 were significantly different (Fig.7), while comparisons of false crawl and nest events one meter adjacent to the crawl tracks were not significantly different (t-test; t = 0.526; p = 0.599; n = 883). It is more likely that turtles were using temperature in the 2008 season when deciding whether or not to nest during a particular excursion because there was a difference in temperature on the tracks of each event despite there being no significant differences in the thermal properties of undisturbed sediment. This implies that there may be seasonal variability in turtle behavior and their use of temperature during nest site selection.

Weather

In 2007 cloud cover seemed to yield the only significant temperature differences on Casey Key. The mean temperatures of wet sand (WS) and dry sand (DS) both within and adjacent to the crawl tracks of nest events were significantly different for factors of cloud cover (WS, DS combined within the crawl tracks: Fig. A8; t-test; t = -2.99; p =

0.003; n = 118; WS, DS combined, one meter adjacent: Fig. A9; t-test; t = -2.69; p =

0.008; n = 118).

The mean temperatures of the water, waterline, body pit, nest chamber, eggs and the gular skin of the female, both within and adjacent to the tracks of nest events, were not significantly different based on factors of rain or cloud cover. Wind was not evaluated for nest events because data were not taken on perceptively windy nights.

105

Figure A8. Box plot of the mean temperatures of wet sand and dry sand (combined within each condition, N and Y) within the crawl tracks of nest events according to the absence (N) and presence (Y) of cloud cover on Casey Key in 2007.

The mean temperature of the water, waterline, wet sand and dry sand within and adjacent to false crawl events were not significantly different based on factors of rain.

Wind and cloud cover were not evaluated for false crawl events because data were not recorded when it a significant amount of wind or cloud cover was perceived.

106

Figure A9. Box plot of the mean temperatures of wet sand and dry sand (combined within each condition, N and Y) one meter adjacent to the crawl tracks of nest events according to the absence (N) and presence (Y) of cloud cover on Casey Key in 2007.

The mean temperatures of the majority of beach locations measured were not significantly different according to weather conditions. Thus, while it is unlikely that weather had any bearing on the behavior of turtles in the 2007 season, the present descriptive study does not have the ability to definitively prove whether various weather conditions have the ability to influence turtle behavior or not.

107

APPENDIX 3 – CASEY KEY: THERMAL DIFFERENCES OVER THREE YEARS

Gular Skin Temperature

The mean temperature of the gular skin of the females was not significantly different among the three seasons (One-way ANOVA; F = 1.12; p = 0.329; n = 163).

Therefore, the temperature of the turtles does not change significantly over time. While the temperature of the turtles remains the same in each season, the mean temperature of the beach sediment does not remain the same, so there was potential for turtles to use sediment temperatures in different ways across seasons.

False Crawl Events

There were significant interannual differences among mean temperatures of the wet sand (WS) and dry sand (DS) within the crawl tracks of false crawl events (WS:

Kruskal-Wallis: H: 6.74; 2 d.f.; p = 0.035; n = 47; DS: Fig. A10; t-test; t = -5.37; p <

0.0001; n = 78). For wet sand, the 2007 and 2009 seasons were similar (Wilcoxon rank sum test; Z = 0.781; p = 0.435; n = 27), while the 2008 season was significantly different from both the 2007 and 2009 seasons (2007, 2008: Wilcoxon rank sum test; Z = -2.00; p

= 0.045; n = 42; 2008, 2009: Wilcoxon rank sum test; Z = 2.21; p = 0.027; n = 25). The

108

dry sand temperature in 2007 was significantly different from the dry sand temperature in

2008 (t-test; t = -5.365; p < 0.0001; n = 78). The 2009 season was not included in the dry sand evaluation because no dry sand temperatures were collected from false crawl events in 2009.

Figure A10. Box plot of the mean temperature of dry sand within the crawl tracks of false crawl events on Casey Key in 2007 and 2008. The 2009 nesting season is not represented here because there was no temperature data collected from dry sand within the crawl tracks of false crawl events.

Adjacent to the false crawls, the mean dry sand temperature remains significantly different between 2007 and 2008 (t-test; t = -5.75; p < 0.0001; n = 78), while there was no interannual difference in mean wet sand temperatures (Kruskal-Wallis; H = 4.58; 2

109

d.f.; p = 0.101; n = 47). The mean temperatures of the water and waterline were not significantly different among the three seasons for false crawl events, neither within, nor adjacent to the tracks.

Turtles that false crawled may have actively searched the wet sand for thermal cues because turtles encountered significantly different wet sand temperatures within the tracks over the three seasons. This suggestion is supported by the insignificant difference of wet sand temperatures adjacent to the tracks. There was no difference in the thermal properties of the wet sand over the three seasons, suggesting the behavior of the turtle is responsible for the thermal differences seen within the tracks. These results are potentially contradicted by dry sand temperatures. Dry sand temperatures were significantly different both within, and adjacent to the tracks of false crawl events. This suggests that the differences seen across the 2007 and 2008 seasons could be solely a function of the shifting thermal properties of dry sand. An alternate interpretation of these results is that turtles may still be actively searching the thermal differences in dry sand, but the thermal properties are also shifting. Therefore, the present study cannot determine if thermal differences seen across the three seasons during false crawl events were due to turtle behavior or the thermal properties of the beach. This study would have to be repeated on Casey Key over several more years to determine what is responsible for the thermal differences seen on this beach.

110

Nest Events

Mean water temperatures were significantly different among the three seasons within the crawl tracks of nest events (One-way ANOVA; F = 7.41; p = 0.0008; n = 173).

A Tukey-Kramer post hoc test showed that mean water temperatures in 2007 and 2009 were similar (p = 0.707), and significantly different from the water temperature in 2008

(2007, 2008: p = 0.004; 2008, 2009: p = 0.009) (Table A2, Fig. A11). The same interannual relationships exist for water temperatures adjacent to the tracks (Table A3;

Tukey-Kramer post hoc test; 2007, 2008: p = 0.002; 2007, 2009: p = 0.309; 2008, 2009:

0.048).

Table A2. Mean temperatures of the sediment and nest locations within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009. Subscripts indicate interannual relationships based on Tukey-Kramer post hoc tests for each beach location, as similar (same letter), or different (different letter).

Temperature (°C ± standard error, ° C) Location 2007 2008 2009

Water 26.2 ± 0.3 A 27.2 ± 0.2 B 26.5 ± 0.2 A

Waterline 23.9 ± 0.3 A 27.5 ± 0.2 B 26.2 ± 0.3 C

Wet sand 23.0 ± 0.4 A 22.6 ± 0.1 A 22.7 ± 0.2 A

Dry sand 23.4 ± 0.2 A 22.8 ± 0.2 A 24.5 ± 0.2 B Body pit and nest chamber combined 24.2 ± 0.4 A 26.5 ± 0.2B 26.5 ± 0.3 B

Eggs 27.2 ± 0.3 A 29.2 ± 0.2 B 28.5 ± 0.2 C

Gular skin of turtle 26.1 ± 0.3 A 26.4 ± 0.2 A 26.6 ± 0.2 A

111

Figure A11. Box plot of the mean water temperature within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009.

Table A3. Mean temperatures of the sediment and nest locations one meter adjacent to the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009. Subscripts indicate interannual relationships based on Tukey-Kramer post hoc tests for each beach location, as either similar (same letter), or different (different letter).

Temperature (°C ± standard error, ° C) Location 2007 2008 2009

Water 26.0 ± 0.3 A 27.0 ± 0.2 B 26.5 ± 0.2 A

Waterline 23.7 ± 0.4 A 27.4 ± 0.2 B 26.1 ± 0.3 C

Wet sand 22.9 ± 0.4 A 22.5 ± 0.1 A 22.6 ± 0.2 A

Dry sand 23.3 ± 0.2 A 22.9 ± 0.2 A 24.5 ± 0.3 B Body pit and nest chamber combined 23.9 ± 0.4 A 22.7 ± 0.2 B 24.1 ± 0.3 A

Eggs 24.6 ± 0.4 A 23.0 ± 0.2 B 23.9 ± 0.3 A

Gular skin of turtle 25.4 ± 0.4 A 22.9 ± 0.2 B 23.9 ± 0.2 C

112

The mean temperature of the waterline was also significantly different among the three seasons within the crawl tracks of nest events (One-way ANOVA; F = 41.3; p <

0.0001; n = 172). A Tukey-Kramer post hoc test showed that mean waterline temperatures from all three seasons were significantly different from one another (2007,

2008: p < 0.0001; 2007, 2009: p < 0.0001; 2008, 2009: p = 0.0001) (Table A2, Fig. A12).

The same interannual relationships exist one meter adjacent to the tracks (Table A3;

Tukey-Kramer post hoc test; 2007, 2008: p < 0.0001; 2007, 2009: p < 0.0001; 2008,

2009: p = 0.0006).

Figure A12. Box plot of the mean waterline temperature within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009.

113

The mean temperature of dry sand was significantly different among the three seasons within the crawl tracks of nest events (One-way ANOVA; F = 17.1; p < 0.0001; n = 355). A Tukey-Kramer post hoc test showed that mean dry sand temperatures in

2007 and 2008 were similar (p = 0.082) and both seasons were significantly different from dry sand temperatures in 2009 (2007, 2009: p = 0.003; 2008, 2009: p <

0.0001)(Table A2, Fig. A13). The same interannual relationships exist among dry sand temperatures one meter adjacent to the crawl tracks (Table A3; 2007, 2008: p = 0.267;

2007, 2009: p = 0.002; 2008, 2009: p < 0.0001).

Figure A13. Box plot of the mean dry sand temperatures within the crawl tracks of nest events on Casey Key in 2007, 2008 and 2009.

114

There was also a significant interannual difference in mean body pit (BP1) and nest chamber (NC1) temperatures within the nest (BP1, NC1 combined: One-way

ANOVA; F = 15.2; p < 0.0001; n = 172). A Tukey-Kramer post hoc test showed that the body pit and nest chamber temperatures in 2008 and 2009 were similar (p = 0.979), while both seasons were significantly different from that of the 2007 season (2007, 2008: p <

0.0001; 2007, 2009: p < 0.0001) (Table A2, Fig. A14). Adjacent to the crawl tracks, there was a different interannual relationship between sediment temperatures. The sediment in the 2007 and 2009 seasons were similar (Table A3; Tukey-Kramer post hoc test; p = 0.966) and both seasons were significantly different from sediment temperatures in 2008 (2007, 2008: p = 0.024; 2008, 2009: p = 0.0005).

Figure A14. Box plot of the mean temperatures of the body pit and nest chamber (combined within each year) of nests measured on Casey Key in 2007, 2008 and 2009.

115

There was a significant interannual difference in mean egg temperatures (One- way ANOVA; F = 23.9; p < 0.0001; n = 169). Mean egg temperatures from all three seasons were significantly different from one another (2007, 2008: p < 0.0001; 2007,

2009: p = 0.0002; 2008, 2009: p = 0.009) (Table A2, Fig. A15). The sediment temperatures adjacent to the eggs were similar between the 2007 and 2009 seasons (Table

A3; Tukey-Kramer post hoc test; p = 0.354) and both seasons were significantly different from the 2008 season (2007, 2008: p = 0.002; 2008, 2009: p = 0.032).

Figure A15. Box plot of mean egg temperatures within all nests measured on Casey Key in 2007, 2008 and 2009.

116

The mean temperature of wet sand was not significantly different among the three seasons within the crawl tracks of nest events (Table A2; One-way ANOVA; F = 0.622; p = 0.537; n = 354). Nor was there a significant difference in wet sand temperatures one meter adjacent to the tracks of nest events (Table A3; One-way ANOVA; F = 0.446; p =

0.641; n = 354).

There was substantial interannual variability in temperature relationships on

Casey Key over three seasons. Some locations on the tracks of nest events were similar for all three seasons (wet sand and the gular skin of the turtles), some locations were different for each season (waterline and eggs), while the remaining locations (water, dry sand, body pit and nest chamber) varied in which seasons were similar to one another

(Table A2). These results may suggest that the searching behavior of turtles was inconsistent over the three seasons. However, the thermal differences of the water, waterline, wet sand and dry sand were maintained one meter adjacent to the tracks (Table

A3). This suggests that the thermal differences on the tracks may have been attributable to the interannual variation in thermal properties of the beach, not the behavior of the turtles.

On the other hand, the relationships among temperatures adjacent to the nest sites

(body pit, nest chamber, eggs, and gular skin of the turtles) varied significantly from the thermal relationships within the nest (Table A2, Table A3). This suggests that the turtles consistently located a nest site thermally similar to their gular skin each season, despite any interannual thermal variation in the sediment near the nest. Because their behavior remained consistent each season despite interannual thermal variation in areas they chose to nest in, they seem to possess the ability to adapt to annual changes in beach

117

temperature. Their behavior may define a biological and plastic decision process, where turtles have a deciding factor, where they compare internal body temperatures to external environmental temperatures, rather than a set threshold parameter of 32°, as suggested for olive ridley turtles by López-Castro (2004). Perhaps their behavior has implications for modeling climate change over time, if eg. turtles can adjust to future global temperature change.

118

APPENDIX 4– TEMPERATURES OF BEACHES WHEN TURTLES WERE NOT

PRESENT

The sediment temperatures of four loggerhead beaches adjacent to Casey Key were also assessed. These beaches were Lido (northernmost beach), South Siesta Key,

North Casey Key (not a part of the study site), and North Venice (southernmost beach).

For each beach, five thermal “profiles” were created by a transect from water to dune or vegetation line and sand temperature was collected every three meters.

There were significant thermal differences among profiles for these beaches (Fig.

A16; One-way ANOVA; F = 21.7; p < 0.0001; n = 220). The mean temperatures of

South Siesta Key, North Casey Key and North Venice beaches were similar (Table A4;

Tukey-Kramer post hoc test). The mean temperature of Lido beach and South Casey Key were similar, but significantly different from these other three beaches (Table A4; Tukey-

Kramer post hoc test). The same thermal relationships were verified one meter adjacent to the profiles as well (Table A4; One–way ANOVA; F = 23.5; p < 0.0001; n =220;

Tukey-Kramer post hoc test).

Sand color may help account for some of the thermal variation among these five beaches. The sand color of Lido and South Casey Key beaches are very similar, but significantly lighter than the color of South Siesta, North Casey Key and North Venice beaches, which are much darker (Fig. A17). Because the sand of South Siesta, North

119

Casey and North Venice beaches are darker, heat energy from the sun is absorbed significantly more than by the lighter sand of Lido or South Casey Key.

Figure A16. Box plot of the mean temperature of all sediment locations measured within the profiles of five beaches known to host loggerhead turtle nesting in southwest Florida in 2009. South Casey Key represents the study site, and the four other beaches are the closest beaches to South Casey Key.

The temperature relationships among these five beaches illustrate the potential for turtles to encounter significantly different temperatures on different beaches, even within the same year. Therefore, any conclusions made in this study may not have predictive power or applicability to other beaches. However, it would be beneficial to continue to

120

investigate these beaches within the same season to see if turtles use thermal cues in a similar way, despite temperature variability across the beaches.

Table A4. Mean sediment temperatures obtained during the 2009 nesting season within and one meter adjacent to five profiles from four beaches closest to the study site (South Casey Key) known to host loggerhead turtle nesting. Subscripts indicate beaches that were thermally similar (share the same letter) and significantly thermally different (do not share the same letter), for each column.

Temperature (°C ± standard error, °C) Beach Name Within the profile One meter adjacent to the profile

Lido 25.5 ± 0.1 B 25.4 ± 0.1 B

South Siesta Key 26.6 ± 0.2 A 26.5 ± 0.2 A

North Casey Key 26.8 ± 0.2 A 26.7 ± 0.2 A

South Casey Key 25.3 ± 0.2 B 25.2 ± 0.2 B

North Venice 27.2 ± 0.2 A 27.2 ± 0.2 A

Figure A17. Sand samples from five beaches in southwest Florida known to host loggerhead turtle nesting. Sample labels are as follows: 1- Lido beach, 2- South Siesta Key, 3- North Casey Key, 4- South Casey Key (study site), 5- North Venice beach.

121

APPENDIX 5 – LITTLE CUMBERLAND ISLAND- 1982

We also had access to data obtained from twenty female loggerhead turtle excursions, 4 false crawl events and 16 nests, from Little Cumberland Island, Georgia,

USA, in the 1982 nesting season. Data were taken using a thermocouple thermometer.

Mean temperatures of false crawl and nest events were significantly different on this beach (t-test; t = 2.42; p = 0.016; n = 272). The mean temperature of false crawl events was 25.0°C ± 0.2°C and the mean temperature of nest events was 25.5°C ± 0.1°C. There was no significant thermal difference among the mean temperatures of all locations measured within the crawl tracks of false crawl events (Kruskal-Wallis; H = 14.9; 13 d.f.; p = 0.308; n = 22). There was, however, a significant thermal difference among mean temperatures of all locations measured within the crawl tracks of nest events (Fig. A18;

One-way ANOVA; F = 10.3; p < 0.0001; n = 95).

Within the crawl tracks of nest events, the nest chamber (NEST HOLE) and ankle deep water (ADW) were thermally similar to all locations measured on the tracks (Table

A5; Tukey-Kramer post hoc test). The mean temperature of the gular skin of the female was significantly different from the mean temperature of the body pit (Tukey-Kramer post hoc test; p = 0.0021). Apart from the nest chamber and ankle deep water, the mean temperature of the gular skin was similar to the mean temperatures of the water and eggs

(Table A5; Tukey-Kramer post hoc test). The mean temperature of the body pit was

122

similar the mean temperatures of the water, waterline, swash zone (SWASH), the grass bank, and the spring high tide line (Table A5).

Figure A18. Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events on Little Cumberland Island, Georgia, USA in 1982.

It seems that turtles nesting on this beach were not searching for a beach temperature similar to their own body temperature. Additionally, many of the sediment temperatures leading up to the nest, including the ankle deep water, waterline, high tide

123

Table A5. Mean temperatures of all locations measured within the crawl tracks of false crawl and nest events on Little Cumberland Island (1982), Wreck Island (2005), Keewaydin Island (2007) and Wassaw Island (2008, 2009). Subscripts indicate locations that were thermally similar (share the same letter) and significantly thermally different (do not share the same letter), for each column.

Little Cumberland Keewaydin Island Island Wreck Island Island Wassaw Island Wassaw Island Wassaw Island Year 1982 2005 2007 2008 2009 2009 False Crawls Event type Nests ** and Nests Nests False Crawls Nests Beach Location* Mean temperature within the crawl tracks (°C; ± standard error)

ADW 26.4 ± 0.6 A, B, C, D, E *** *** *** *** ***

BERM *** 26.7 ± 1.2 A *** *** *** ***

124 BERM FOOT *** 28.3 ± 1.6 A *** *** *** *** *

BP1 26.0 ± 0.2 C, E 28.2 ± 0.4 A (A) 24.2 ± 0.8 B, C 24.5 ± 0.8 A, B *** 24.4 ± 0.6 B, C, D

BP2 *** 27.9 ± 0.8 A *** *** *** ***

BP3 *** 24.3 ± 1.2 A *** *** *** ***

DS *** 27.4 ± 1.2 A 21.9 ± 0.2 C 23.8 ± 0.2 B *** 22.3 ± 0.5 D

DUNE *** *** 22.6 ± 0.6 C 24.1 ± 0.7 A, B *** 22.4 ± 1.6 A, B, C, D

EGG 28.6 ± 0.6 A *** 27.2 ± 0.5 A, B 23.4 ± 0.7 A, B *** 27.3 ± 0.6 A

GRASS BANK 24.4 ± 1.0 B, C, D, E *** *** *** *** ***

GULAR 27.3 ± 0.2 A, B 27.5 ± 1.6 A 26.8 ± 0.4 A, B 23.8 ± 0.6 A, B *** 24.8 ± 0.5 A, B, C * HTL 24.5 ± 0.3 D 26.2 ± 0.5 A (B) 22.2 ± 0.3 C 23.2 ± 0.6 B 18.8 ± 1.8 C 23.7 ± 0.5 C, D

HTL/W *** 26.3 ± 1.6 A *** *** *** ***

MHW *** *** 22.0 ± 1.8 A, B, C *** *** ***

NC1 *** *** 27.4 ± 0.7 A, B 27.0 ± 1.0 A *** 28.3 ± 1.6 A, B, C

NEST HOLE 26.8 ± 1.0 A, B, C, D, E *** *** *** *** ***

Table A5 (cont.)

Little Cumberland Keewaydin Island Island Wreck Island Island Wassaw Island Wassaw Island Wassaw Island Year 1982 2005 2007 2008 2009 2009 False crawls Event type Nests ** and Nests Nests False Crawls Nests Beach Location* Mean temperature within the crawl tracks (°C; ± standard error)

ROCK *** 24.3 ± 1.2 A *** *** *** ***

SHTL 24.5 ± 0.6 D, E 26.3 ± 0.7 A 21.5 ± 0.9 C 22.5 ± 1.2 A, B 22.3 ± 1.8 A, B, C 22.9 ± 0.9 C, D

SHTL/DS *** 27.9 ± 1.6 A *** *** *** ***

SLOUGH *** *** *** *** *** 24.2 ± 1.1 A, B, C, D 12 SWASH 25.9 ± 0.3 *** *** *** *** *** 5 C, E

* W 27.0 ± 0.3 A, B, C 26.5 ± 0.4 A (B) 27.3 ± 0.3 A 24.6 ± 0.5 A, B 26.6 ± 1.0 A 26.9 ± 0.6 A, B

WL 24.8 ± 1.0 B, C, D, E *** 26.7 ± 0.3 A, B 24.0 ± 0.5 A, B 24.9 ± 1.0 A, B 24.4 ± 0.5 B, C, D

WRACK *** *** *** *** *** 22.4 ± 1.1 C, D

WRACK/SHTL *** *** *** *** *** 27.7 ± 1.6 A, B, C, D

WS *** 26.5 ± 0.7 A 22.1 ± 0.2 C 22.9 ± 0.3 B 22.3 ± 0.3 B, C 23.2 ± 0.2 C, D

WS/SLOUGH *** *** *** *** *** 24.0 ± 0.8 A, B, C, D * See Table 6 for a description of most locations; ADW: ankle deep water; MHW: mean high water **False crawl and nest events were not indicated when data were collected; all events treated together ***This location was not available or not measured on the beach or in the year indicated * A (A) or A (B) indicate the primary post hoc test result (outside of parentheses) and secondary post hoc test result (within parentheses)

line, spring high tide line, and the grass bank were thermally similar (Table A5; Tukey-

Kramer post hoc test), indicating that turtles may not have been able to thermally discriminate among various locations on the beach. These results may also imply that turtles nesting on Little Cumberland Island did not utilize temperature as a nest site selection cue in the 1982 season.

On the other hand, turtles may have used temperature when deciding to false crawl or nest because the mean temperatures of these two types of events were significantly different. However, no temperature data were collected adjacent to the tracks, which could have verified this speculation. Another thermal study similar to the present one must be performed on this beach, and all other beaches presented in the present study, over several years to determine how temperature may be used by loggerhead turtles over time. One season of thermal data is not indicative of turtle behavior every season on a single nesting beach, or all loggerhead nesting beaches.

Little Cumberland Island has a beach with a relatively flat foreshore with a maritime forest atop high, steeply scarped foredunes. It is likely that slope or proximity to the high dunes has a profound influence on nest site selection on this beach, because the high dunes are a dominant feature of this beach. Therefore, slope may have superseded the importance of thermal cues. A future study should investigate if loggerheads nesting on the Archie Carr National Wildlife Refuge and Little Cumberland

Island behave similarly, to confirm if dominant beach features, such as steeply scarped foredunes, a feature shared by both of these beaches, are primary drivers of nest site selection.

126

APPENDIX 6 – WRECK ISLAND- 2005

We also analyzed data from 21 events collected from loggerheads emerging onto

Wreck Island, 93 km north east of Gladstone, Queensland, Australia, from the 2005 nesting season. It was unclear whether these events were false crawl or nest events in each case, therefore they were all analyzed together.

While there was a significant omnibus test (One-way ANOVA; F = 2.16; p =

0.023; n = 74), a Tukey-Kramer post hoc test did not reveal any significant differences among the locations measured within all events (Table A5). Therefore, a secondary One- way ANOVA test was performed where only locations with the greatest sample size, including the water (n = 16), high tide line (n = 13), and the body pit (n = 19), were used.

This test revealed that there was a significant thermal difference among these three locations (Table A5; One-way ANOVA; F = 6.59; p = 0.003; n = 48). The water and high tide line temperatures were similar (Tukey-Kramer post hoc test; p = 0.885) and significantly different from the body pit (Fig. A19; BP1, W: p = 0.016; BP1, HTL: p =

0.007).

The primary Tukey-Kramer post hoc test revealed that the mean temperature of the gular skin of the turtles was similar to that of all locations, including the mean temperature of the body pit. However, this result does not necessarily suggest that turtles were actively seeking a temperature similar to their body temperature, because all mean

127

Figure A19. Box plot of the mean temperatures of the body pit (BP1), high tide line (HTL), and water (W) within the crawl tracks of all events measured on Wreck Island, Australia in 2005.

temperatures that were measured were similar the turtle’s body temperature. Because the use of thermal cues by loggerheads on Wreck Island is unclear, it may suggest that there are other environmental cues considered when they choose a nest site, either in addition to, or instead of temperature. However, the secondary post hoc test showed the potential for turtles to search for a specific temperature because the body pit was significantly different from the high tide line. However, it would be best to perform another study similar to the present study on this beach to determine the use of temperature by

128

loggerheads on Wreck Island. The present one does not provide clear evidence as to how temperature is used by loggerheads on this beach.

Wreck Island is mainly formed from beach rock, with a relatively low slope and large beach width. Vegetation in the back beach consists mainly of a Pisonia forest comprised of both Bircatcher tree (Pisonia brunoniana) and cabbagetree (Pisonia grandis). Because Wreck Island has such a large width, turtles may have to crawl a long distance to nest, and subsequently be on the beach for a relatively long period of time, taxing the energy reserves of the turtles. Therefore, beach width may be a more important cue to gravid females on this beach, as distance traveled can impact their parental fitness. Beach width (Garmestani et al., 2000; Mazaris et al., 2006; Serafini et al., 2009) has been implicated as influencing nest site selection in sea turtles.

129

APPENDIX 7 – KEEWAYDIN ISLAND- 2007

We had access to temperature data from 35 false crawl events and 47 nest events from loggerhead turtles nesting on Keewaydin Island, Florida, USA, in the 2007 nesting season. The mean temperatures obtained from false crawls and nests were not significantly different (t-test; t = 0.493; p = 0.622; n = 755). The mean temperature of false crawl events was 23.5°C ± 0.2°C and the mean temperature of nest events was

23.7°C ± 0.2°C. Among all events measured, there was a significant temperature difference in the mean temperatures of the locations measured (Fig. A20; One-way

ANOVA; F = 55.1; p < 0.0001; n = 753).

The mean temperature of the mean high water was similar to all locations measured on the crawl tracks of false crawl and nest events (Table A5; Tukey-Kramer post hoc test). The gular skin of the turtles was also similar to the mean temperatures of the water, waterline, body pit, nest chamber and eggs (Table A5; Tukey-Kramer post hoc test). Additionally, it seems that many of the sediment locations leading up to the nest or apex of the false crawl were thermally similar, including wet sand, dry sand, high tide line, spring high tide line, and the dunes (Table A5; Tukey-Kramer post hoc test).

It seems gravid females nesting or attempting to nest on Keewaydin Island do not use thermal cues to decide whether to nest or not (because there is an insignificant difference between mean temperatures of false crawl and nest events). Also, it does not

130

appear that turtles use differences in temperature on the nesting beach to search for a nest site (because most sediment temperatures on the nesting beach were similar). They do, however, seem to seek out a temperature on the nesting beach thermally similar to her own body temperature (because the temperature of her gular skin and the body pit are similar). Therefore, turtles did seem to incorporate temperature into their decision making process this season, but another temperature study would have to be performed to determine if they used this environmental cue habitually, as turtles on Casey Key did.

Figure A20. Box plot of the mean temperatures of all locations measured within the crawl tracks of false crawl and nest events on Keewaydin Island, Florida, USA, in 2007.

131

Keewaydin Island has a relatively flat beach and a relatively narrow width, with vegetation covering the backshore. Vegetation species found on Keewaydin Island include sea oats (Uniola paniculata), gumbo limbo (Bursera simaruba), cabbage palm

(Sabal palmetto), Jamaican dogwood (Piscidia piscipula), buttonwood (Conocarpus erectus), nakedwood (genus Colubrina), tough buckthorn (Sideroxylon tenax), hercules club (Aralia spinosa), coco plum (Chrysobalanus icaco), bay cedar (Suriana maritima), sea grapes (Coccoloba uvifera) and snowberry (Symphoricarpos oreophilus). In addition to temperature, turtles may incorporate proximity to vegetation into the nest site selection process. Proximity to supralittoral vegetation (Hays and Speakman, 1993; Hays et al.,

1995) has been implicated as influencing nest site selection in sea turtles.

132

APPENDIX 8 – WASSAW ISLAND- 2008 AND 2009

2008 Nesting Season

In the 2008 season on Wassaw Island, Georgia, USA, data were collected from 2 false crawl events and 12 nest events. There was a significant difference in mean temperatures collected within the crawl tracks of false crawl and nesting events (t-test; t =

-2.26; p = 0.025; n = 204). The mean temperature of false crawl events was 24.3°C ±

0.3°C and the mean temperature of nest events was 23.6°C ± 0.1°C. Among locations measured within the crawl tracks of the false events, there were no significant thermal differences (Kruskal-Wallis test; H = 11.1; 7 d.f.; p = 0.136; n = 34). There were, however, significant thermal differences among temperatures collected from locations within the crawl tracks of nest events (Fig. A21; One-way ANOVA; F = 2.89; p =

0.0025; n = 150).

The mean temperature of the gular skin of the females was similar to the mean temperatures of all locations measured within the crawl tracks of nest events, including that of the body pit (Table A5; Tukey-Kramer post hoc test). Additionally, all sediment locations were thermally similar, including the waterline, wet sand, dry sand, high tide line, spring high tide line and dunes (Table A5; Tukey-Kramer post hoc test).

133

Figure A21. Box plot of the mean temperatures of all locations measured within the crawl tracks of all nest events measured on Wassaw Island, Georgia, USA in 2008.

Because the mean temperature of the gular skin of the females and the body pit are similar, it is possible that the turtles were searching for a temperature similar to their own to choose a nest site. It is difficult to determine the validity of this statement because the mean temperatures of many other locations on the beach were also thermally similar to the gular skin of the females (Table A5). Even if temperature was used as a nest site selection cue on Wassaw Island this season, temperature could not have been the only cue used to make the decision, because turtles encountered many other locations

134

thermally similar to their body temperature before they nested, such as wet and dry sand locations, and the high tide and spring high tide lines. If temperature were the only deciding factor, the turtles should have chosen to nest at one of these locations alternatively. Therefore, at least one other cue, but more likely a suite of cues, must have been incorporated to make the most well informed nest site decision.

2009 Nesting Season

In the 2009 Wassaw Island nesting season, data were collected from four false crawl events and 12 nest events. There was a significant difference in mean temperatures collected within the crawl tracks of these two types of events (t-test; t = 4.13; p < 0.0001; n = 226). The mean temperature of the false crawl events was 22.4°C ± 0.3°C and the mean temperature of nest events was 23.8°C ± 0.2°C.

False Crawl Events

There was a significant difference among the mean temperatures collected within the crawl tracks of false crawl events (Fig. A22; One-way ANOVA; F = 6.33; p =

0.0005; n = 45). The mean spring high tide line temperature was similar to all locations measured on the false crawl tracks (Table A5; Tukey-Kramer post hoc test). The mean water temperature was only similar to the mean waterline temperature, but the waterline temperature was also similar to the wet sand temperature (Table A5; Tukey-Kramer post hoc test). The mean wet sand temperature was also similar to the high tide line temperature (Table A5; Tukey-Kramer post hoc test).

135

Figure A22. Box plot of the mean temperatures of all locations measured within the crawl tracks of all false crawl events measured on Wassaw Island, Georgia, USA in 2009.

Despite significant temperature differences within the false crawl tracks, most of the sediment locations on the tracks (wet sand, high tide line, spring high tide line) were thermally similar. This result may indicate that turtles did not search for differences in temperature during a false crawl event. However, temperature data from Casey Key and

Keewaydin Island have shown that despite similar sediment temperatures on the nesting beach, turtles still sought a temperature similar to their gular skin. Therefore, turtles may have been unable to locate a temperature thermally similar to their own on Wassaw

Island in 2008, causing a false crawl event. Alternatively, turtles may have used another

136

environmental cue, other than temperature, to determine that the excursion was not conducive to nesting.

Nest Events

There was also a significant difference among the mean temperatures of the locations measured within the crawl tracks of the nest events (Fig. A23; One-way

ANOVA; F = 7.20; p < 0.0001; n = 121). The mean temperatures of the slough, dunes, and locations with a combination of wet sand and slough, and wrack debris on the spring high tide line, were similar to all locations measured on the tracks (Table A5; Tukey-

Kramer post hoc test). The mean temperature of the gular skin of the turtles was also similar to the mean temperature of most locations measured on the tracks, including that of the water, waterline, wet sand, the high tide line, the spring high tide line, wrack debris, body pit, nest chamber and eggs (Table A5; Tukey-Kramer post hoc test).

Sediment temperatures leading up to the nest were all similar to one another, including the waterline, wet sand, dry sand, the high tide line, spring high tide line, wrack debris, the spring high tide line with wrack debris, slough, the location of the slough that also incorporated wet sand, and the dunes.

It is possible that turtles nesting on Wassaw Island in 2009 used temperature as a cue when deciding to nest or false crawl, and they may have searched for a temperature on the beach that was similar to their own as a suitable nest location. It seems unclear however, just as in the 2008 season, whether turtles were able to use temperature to discriminate among beach locations because the majority of sediment temperatures from false crawl and nest events were thermally similar. A thermal study similar to the present

137

study would need to be repeated over several more years, at least, to determine how turtles may use temperature on each nesting beach over time.

Figure A23. Box plot of the mean temperatures of all locations measured within the crawl tracks of nest events measured on Wassaw Island, Georgia, USA in 2009.

Wassaw Island is a relatively flat beach with a narrow width, a maritime forest and large tree branches that litter the foreshore. Additional nest site selection cues could include proximity to fallen tree debris, or proximity to vegetation. Other characteristics of the sand, such as sand grain size (Yalçin-Özdilek et al., 2007), compactness

138

(Ackerman, 1997), porewater content (Chen et al., 2007), or organic content (Mazaris et al., 2006), which have all been suggested as important nest site selection cues, could also be important to turtles nesting on Wassaw Island or any other rookery. One or more of these should be considered in a future study.

Wassaw Island: 2008 vs. 2009

Between these two nesting seasons, there was no significant differences among mean temperatures of the body pit of the nest (BP1), nor the mean temperature of the gular skin of the nesting females (GULAR) (BP1: Wilcoxon rank sum test; Z = 0.599; p

= 0.549; n = 12; GULAR: t-test; t = 1.48; p = 0.158; n = 18). This suggests that nesting turtles may have sought out a similar temperature on the nesting beach both seasons, concurring that turtles may indeed be seeking a certain temperature when locating a nest site. But what remains to be determined is how they choose a certain location for the body pit when many other locations on the nesting beach, such as wet sand, the high tide line and the spring high tide line, in both seasons, were also thermally similar to the nesting turtle. It is beyond the scope of this study to determine what other factors may be at play on the beaches other than Casey Key, but it is very important to investigate in future studies.

139